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THEORY AND PRACTICE 



OF 



THE ELECTRIC TELEGRAPH 



A MANUAL 



For Operators and Students, 



BY 



CHARLES H. CHURCHILL, 



FliOFESSOK OF NATIIIM, Fill I.OSOFIIY. 



ODERLIN COLLEGE. /u 



mi 



OHEKLIN, OHIO \ 

SHERMAN & BROS., PUBLISHERS. 



^v. 



N 



•eh 



Entered, aeeordiug to Aci of Congress, in the year 1ST3. 
By C. A. SHERMAN. 

In the Office of the Librarian of Congress, at Washington. 



% 



y 




PF.IXTED BY 

', H. BATTLE & CO: 
OBERIJ>*i onir, 



PREFACE. 

THE number of very admirable works published of late, on the 
subjects treated In this manual, might seem to render its 
appearance quite unnecessay. The particular form, however, in 
which it is written, has been asked for by skillful teachers in the 
Telegraphic Colleges, and the work meets, therefore, only an 
imperative demand. 

To students not already trained by a thorough general acquaint- 
ance with scientific subjects, the form of question and answer 
presents the readiest means of investigation, and of satisfaction, 
also, provided the questions are arranged in a natural and pro 
grcssive order. 

At the same time it precludes the construction of those con- 
densed and comprehensive sentences that are often the delight of 
the advanced scholar. 

At the risk of some repetitions, the answers in nearly all cases 
arc so worded that the cursory reader may omit the questions 
entirely without losing the sense or the connection. 

As to the subject matter a few departures from common method 

may be noted. First, language adapted only to theories not now 

generally deceived, is, as far as possible, discarded. Second. 

The idea of polar forces, and the principle of inductive action are 

made prominent early in the work so that each phenomenon may 

be explained as it occurs rather than in a general chapter at the 
end. 

A little more attention is given to the secondary current than is 
usual in telegraphic manuals, the discoveries of Mr. Elisha Gray 
having brought the subject into new prominence. 

Historical details have been for the most part omitted or briefly 
touched as the limit of such a work would permit. 

In the chapters on practical telegraphy T have drawn lVcely from 
the works. of Pond, Mattison, Pope and others who have written 
with much acceptance in this department. C. H. C. 



CHAPTER I. 

Sec. i. Magnetism. 2. Mag. Needle. 4. Law of Mag 
nets. 6. Magnetics. 7. Coercive force. S. Induction, Arti- 
ficial Magnets made. 9. Dia-magnetics. 10. Successive 
inductions. 11. Armatures. 12. Astatic needle. 13. Theo- 
ries of magnetism. 

CHAPTER II. 

Sec. 1. Two kinds of electricity. 2. Electrics. 3. Law of 
electricity. 4. Transference of electricity. 5. Separation of 
electricities. 6. Development of electricity by friction. 7. 
Electroscopes. 8. Experiments. 9. Spheres of communica- 
tion and of influence, to. Conductors. 11. Table of con- 
ductors and insulators. 12. Theory of induction. 13. Dielec- 
trics. 14. Specific induction. 15 and 32. Electric machines. 
16. Experiments. 17. Intensity and quantity. iS. Electric 
tension. 20. Discharge. 21 and 2c;. Connection with the 
ground. 23. Free electricity. 24. Ratio of intensity and 
quantity. 25. Enlarging one conductor. 26. Diversion of 
influence. 27. Permanent charge. 28. Effect of insulation. 
29. Distribution of charge. 31. Experiments. 33. Electro- 
phorous. 34. Condensation. 3^, Leyden jar. 36 Cascade 
series. 37. Quantity in a charged jar. 38. Discharge by 
installments. 39. Triple jar. 40. Automatic discharge. 43. 
Electric battery. 44. Use of the coatings. 45. Polarization 
of the glass. 46. Residual charge. 47. Disguised electricity. 
4S. Light from electricity. S°- Force from electric dis- 
charges. 51. Sound. 52. Lightning rods. 54. Branches of 
electric science. 

CHAPTER III. 

Sec. 2. Voltaic battery. 3. Electric condition of plates. 
4. Effect of closing circuit. 5. Electric current. 6. Incon- 
stancy of the battery. Smee's battery. 7. Local action. S. 
Two fluid battery, Grove, Daniell and Bunson. 9. Quantity 
battery. 10. Intensity batterv. 



IX 
CHAPTER I \ 

SfiC. i. Electro-magnet. 2, Helix. 3. Relation of poles 
to the current. 4. The solenoid. 5. Ampere's theory. 6. 
Permanency of electro-magnets. 7. Power of electro-mag 
nets. 9. Electro-moters. 10. Practical uses. 11. Oersted's 
discovery. 12. Galvanometer. 

CHAPTER V. 

Sec. 1. Electro-magnetism. 2. Primary and secondary 
currents. 3. Currents of the third and higher orders. 4. 
Extra currents. 5. Induction coils — inductorium. 

CHAPTER VI. 

Sec. 1. Definition and History. 2. Telephone. 3. The 
Morse system. Description of the Morse instrument. Key. 
page 46. Register, page 47. Relay and Sounder, page 48. 
Switch, page 50. Register, page 52. 



CHAPTER I— BATTERIES. 

Sec. 1. Care of batteries. 2. Daniclfs battery and Cal- 
laud's. 3. Care of the Grove battery. 4. Care of Hansen's 
batterv. 

CHAPTER II. 

Sec. 1. The key. 2. The relay. 4. The sounder. 5. The 
register. 6. The arrester. 7. The repeater. 

CHAPTER III. 

Sec. 1. Key movements. 2. Morse's Alphabet analyzed. 
3. The telegram. Examples. Checking. Examples in 
checking. 4. The office call. ^. Cautions respecting the 
copy, the address, the record etc. 

CHAPTER IV. 

Sec. 1. Train reports. 2. Forms of train orders. Exam- 
ples. 

CHAPTER V. 

Sec. 1. Repeaters, Wood's button repeater, Hick's re- 
peater, Millikcn's repeater, Bunnell's repeater, 2. Local 
circuit chancer. 



CHAPTER VI. 

Sec. i. Character and causes of resistance. Effect of 
resistance. Effective force. 2. Measurement. Unit of 
resistance. Rheostat. Unit of force. Unit of quantity. 
Unit of current. 

CHAPTER VII. 

SEC. I. Break. 2. Escapes and crosses. Grounds, 
Weather crosses. 3. Reversed batteries. 4. Electrical dis- 
turbances. Storms. Earth currents. Earth battery cur- 
rents. 

CHAPTER VIII. 

Sec. 1. Testing for a break. 2. Location of a break. 3. 
Testing for an escape. 4. Testing for crosses. Location of 
a cross. 

CHAPTER IX. 

Sec. 1. Advantage of this method. 2. The instruments 
used. 2. Practice with the galvanometer. Proper amount, 
of resistance. High and low resistance. 4. Loop test's. 
Rules and examples. 6. Location of crosses by measure. 
Culley's method. Blavier's method. 

CHAPTER X. 

Sec. 1. Electromotive force. Effect of size of cell. Branch 
circuits. Joint resistance of branches. Resistance of batteries 
and short wires. 3. Application of Ohm's law. Pope's 
example. 4. Blavier's method without a loop. Examples. 

CHAPTER XL 

Sec. 1. Conductivity. Rules. Examples. 
CHAPTER XII. 

Sec. 1. Essential parts of the line. Insulators and crossbars. 
Use of glass. Other materials. 2. The line wire. Size. 
Material. Splicing. 3. Strain of wires. Rule for dip. 

CHAPTER XIII. 

Sec. 1. Receiving instruments. 5. Operation of conden- 
ser. 7. Rate of signals. 6. Detection and location of faults. 
7. Detection and location of faults while laying cable. 
Minute examination at the factory. 



XI 

CHAPTER XIV. 
ist. Wires entering an office. 2d. Relative situation of bat- 
teries and instruments at a terminal station. 3d. Relative 
situation of batteries and instruments at way stations. 

APPENDIX. 

A.— Clark's double shunt galvanometer. 

B. — 'Internal resistance of different batteries, p. 13!. 

C. — Electrostatic capacity. 

D.— Measurement of force, p. 132. 

E.— -Spontaneous discharge of the cable, p. 134. 

G.— Electric light, p .134. 

H. — -Thermo-electricity, p. 135. 

I. — The Automatic Telegraph, p. 136. 

J. — Qiiantit3' and Intensity, p. 13S. 

Temperature, p. 119. Joint resistance, p. 139. Explana- 
tion of tables, p. 140. iron, p. 140. 

TABLES. 
Table I. — Force of Batteries, p. 141. 
Table II. — " " in volts, p. 141. 

Table III. — Conducting power of different metals, p. 142. 
Table IV. — Resistance of different wires in ohms, p. 142. 
Table V. — Relative resistance and weights of wire, p. 143. 
Table VI. — Units of length, resistance, tension, quantity 

and current. 






GLOSSARY OF TERMS. 



Ampere's Theory. — Magnets are constantly traversed by electric 

current?. See p. 35. 

Anode. — Positive pole of a battery. 

Armature. — Short bar across the ends of a horse-shoe magnet. 

Astatic. — Without directive power. 

Atoms. — The infinitely small particles of which all bodies are sup- 
posed to be made up, and which are capable of motion among 
themselves. 

Aurora Borealis. — Electric streamers in the upper atmosphere. 

Austral Magnetism.— That developed at the south magnetic pole 
of the earth. 

Battery. — In frictional electricity, a set of Leyden jars connected 
together. 

In voltaic Electricity. — One or more cells charged with the proper 
materials to produce a current. 

Boreal Magnetism. — The magnetism of the northern magnetic 
pole of the earth. 

Bunsen Battery. — Carbon batter, invented by Bunsen. 

Capacity. — The quantity of electricity a jar, cable or other con- 
denser can contain. 

Cathode. — The negative (or zinc pole; of a battery. 

Charge. — verb.) To give a jar or cable its full quantity of elec- 
tricity. 

Charge. — (noun.) The electricity contained in any condenser. 

Checking. — Attaching to a message a record of the number of 
words and of the tariff due or paid. 

Circuit. — The whole path of a current from one pole of a battery 
around to the same point again. 

Condenser. — Metallic plates arranged to act inductively on each 
other. 

Dia-magnetic. — The non-conductor through which a magnet acta 
inductively. 

Dielectric. — The air or other non-conductor through which elec- 
tricity acts inductively. 

Disguised Electricity.— That which does not affect an electro^ 
scope. 



XIII 

Electro-magnet. — Soft iron, surrounded by wires which have been 
previously varnished or else covered with silk or cotton. 

Electro-motor. — An engine propelled by an electro-magnet. 

Electric Storm. — Unusual development of atmospheric electricity. 

Electro-type. — An engraving or any device for printing, which is 
reproduced in copper by the process of electro-plating. 

Electro-plating. — Depositing on any surface, a plate of copper or 
other metal, by electricity. 

Extra Current. — Current induced on the parallel coils of a single 
wire by the primary current on the same wire. 

Farad. — The unit of force in electricity. 

Free Electricity. — Either electricity separated from its opposite. 

Galvanic. — Eesulting from Galvani's discoveries. (The same as 
voltaic in practice.) 

Galvanometer. — An instrument for measuring the force and direc- 
tion of a current. 

Helix. — (plural helices.) Wire bent in a spiral form. 

Induction. — The excitement of one kind of electricity or of mag- 
netism by its opposite. 

Inductorium. — A large induction coil. 

Insulation. — The separation of a body from all others by glass, air, 
or other non-conductors of electricity. 

Key.— Instrument for opening or closing circuit. 

Local Battery. — The battery used at a way station for registering 
the message. 

Local Circuit. — The path traversed by the current of the local bat- 
tery. It is confined to the office where the battery is. 

Magnetic field. — The region or space throughout which a given 
magnet acts. 

Main Battery. — That used at terminal stations. 

Main Line. — The through wire between terminal stations. 

Meridian. — (magnetic.) The direction assumed by the magnetic 
needle. 

Meridian. — (geographical.)— The true north and south line through 
any point. 

Ohm.— Unit of resistance. - 

Opening the Circuit.— Breaking contact so as to arrest the cur- 
rent. 

Polarize.— To separate the two polar forces of a body. 

Polarity. — Opposite forces of equal magnitude developed at the 
opposite ends of a given line called the axis. 

Poles. — Points of maximum force in the opposite ends of a magn< i 
or a battery. 



XIV 

Positive Plate. — The copper, carbon or platinum plate, from which 

(in the air,) the -f current always flows. 
Potential. — (electric.) Comparative electric intensity of a given 

point. 
Residual Charge. — Left after the discharge of the Leyden jar. 
Register- — The Morse recording instrument. 
Relay. — An instrument attached to the main line for opening and 

closing a local circuit. 
Resistance. — The opposition of any conductor to the flow of the 

current. 
Rheostat. — A collection of resistance coils. 
Sounder. — Instrument for reading a message by ear. 
Spacing. — Practice in the proper separation of dots and dashes. 
Secondary Current. — Current induced in a separate parallel wire 

hj the current of a primary wire. 
Shunt. — A branch circuit. If a bow-string represents a line wire, 

a portion of the current might be shunted by a separate wire 

around by the bow. 
Solenoid. — A helix delicately suspended to act as a magnetic 

needle. 
Telegram. — Anything sent by telegraph. 
Thermo-electricity. — Electricity excited by heat. 
Vertical Line. — The direction assumed by a plumb-line. 
Volt.— The unit of force. About the force of one Daniell's cell. 
Voltaic. — Resulting from the discoveries of Volta, an Italian. 
Volta-meter. — An instrument for measuring the electro-motive 

force of a batter v. 



Signals. — The following signals are in common use upon 
railroad telegraphs. A few of them are also quite extensively 
used on commercial lines: 

i. — Wait a minute. 13. — I (or we) understand. 

2. — Important. Train orders. 18. — What is the matter. 

3. — Give me correct time. 22.— Busy on another line, 

4. — Where shall I go ahead. 33. — Answer prepaid. 

5. — Anything for me? 44. — Answer immediately. 

7L — Keep circuit closed. 73. — Accept my compliments. 

S. — I have business for you. 134. — Who is at the key. 

9. — Train Dispatcher's signal, has preference over everything. 

12. — Is it O. K.? or, How do you understand? 

Q. & E.— Conductor and Engineer. 



XV 

Abbreviations. — The number of words, everywhere alike 
abbreviated, is quite small. The table contains the few 
which are more commonly employed; others may be readily 
understood from their connection in most cases. 

ABBREVIATIONS. 



Al) v.— Above. 
Ads.— Address. 
Ah r.— Another. 
Am t. — Amount. 
Ans.— Answer. 
Ar.— Arrived. 
Brk.— Break. 
Bsns.— Business. 
Cc— Commence. 
Cd.— Could. 
Ui.~ Circuit. 
Co.— Companv. 
Condr. — Conductor. 
(Jhgs.— Charges. 
Dep.— Departed. 
Dg.— Doing. 
Dw.-- Down. 
D. II.— Dead Head. 
Ehr.— Either. 
Ex.— Express. 
Fr.— From. 
Fit.— Freight. 
Fwd.--- Forward. 
Guar.— Guaranteed. 
G. A.— Go Ahead. 
(Jg,— Going. 
Gl --Give. 
G. M.-- Good Morn in; 



G. X.— Good Night. Gone. S. F. B.— Stop for breakfast. 
G.— Ground. S. F. D. '• dinner. 

Ww.— How. S. F. T. ■« tea. 

Emmy.— Immediately. S.F.N. '• night. 

Inst.— Instrument. Instant. Stk. Stock. 



K\v. — Know. 
Msk.— Mistake. 
Msg. — Message. 
Msngr. — Messenger. 
Nn.— None. 
No.— Number. 
N sy - — N ecessa ry . 
O. K.— Correct, 

Ofs.— Office. 
Ohr.— Other. 
Opr. or Op.— Operator. 
« ►. S— Oh say. 
Fa.— Fay. 
Pis.— Please. 
Psb.— Possible. 
Qk.— Quick. 
Rr.— Repeat. Railroad. 

Rtn.— Return. 

Sd.— Should. 

SI.— Shall. 

Ss.— Says. 



Smtg.— Something. 
Stix.— Sticks. 
T.— The. 
Tt.— That. 
Td.— To-day. 
Tff.— Tariff. 
Tk.— Think. 
Tnk.— Thank. 

Tm —Them. To-morrow 
Trn. --Train. 
Thru.— Through. 

U— You . 
Ur.— Your. 
Uu.— Under 

Und.- -Understand. 
V.— Very. 

Wk.— Weak. Week. 
W n .—When. 
Wt.— What. 
X.— Next. 



Words having certain terminations are also abbreviated in 
the following manner: Termination ing omits in; cd, e 
or tan, io or ia; ive, ic; ial, ia; die, c; fid, u; and ess, s. 



ion 



CORRECTIONS. 



1. A laic rule agreed upon by the telegraph companies varies 
from that given under question 2, in the directions for cheeking 
on page 65. The new rule excludes from the address everything 
except the mere name, all else is counted and charged in the tariff. 

2. On page 12, at the end of the answer to question 3d, under f 
13, read, "Shellac is a poorer insulator than air." 

3. On page 86, third line from the top omit only, 

4. Page 130, 27th line. Read Fig. 62 for Fig 60. 
Same on p, 137, 8th line. ' 



FRONTISPIECE. 
THE MORSE ALPHABET. 

Prof. Smith's Six Principles, 

First. Dots close together. 

I S H P 



Second. Dashes close together 

M 5 

Third. Lone dots. 



Fourth. Lone dashes. 

T L or cipher, 



Fifth. A dot followed by a dash. 

A 

Sixth. — A dash followed by a dot. 

X 

L or cypher TEISHP 6 A 

U V 4 X D B 8 G 

7 F Comma X W I Q_ 



2 


Period 




3 




M 




5 


Interrogation 


9 


K 


J 




O 




R 


& 


C 


Z 



These characters, forty in number, are formed of three 
simple elementary marks: the dot, the short dash, and the 
long dash. These elements, uncombined, are respectively E. 
T, and L or cipher. The remaining thirty-seven are made 
up of the dot and the short dash, the long dash never being 
used in combination, nor repeated except to repeat the letter 
or figure which it represents. 

NOTE 1. Instead of the sign for italic-, operators usually empha- 
size by spacing more widely the letters of a word. 

2. The sign for parenthesis precedes and follows the words 
referred to. It is seldom used. 

■ '>. The period answers in almost all eases for the semicolon. 

4. For directions and exercises in the alphabet see page <>2 



CHAPTER I. 

nyr^o-isrETisnyi:. 




1. The 3Iagnet.~l. What is a magnet? 

A certain ore of iron (first bro'ight into notice near Mag- 
nesia in Asia) which has the property of attracting and hold- 
ing small pieces of iron is called the natural magnet or load- 
stone. 

2. What is au artificial magnet? 

A bar of steel prepared for the purpose which has the 
same power as a loadstone is an artificial magnet. 

3. What arc the poles of a magnet? 

If a magnet be rolled in iron 
filings they will adhere to it in 
thick masses at two opposite 
points called the poles. 

4. What is the central point? 

At a point about midway between the poles the filings do 
not adhere ; this is called the neutral point. 

5. What is the axis of a magnet? 

A straight line joining the poles is called the axis. 

2. The Needle.— 1. What is the magnetic needle? 

A thin bar-magnet, pointed at the ends and properly bal- 
anced on a pivot is called a magnetic needle. 

2, AVhat property is revealed by the needle? 

A magnet thus suspended will take a fixed direction with 
respect to the earth, called the magnetic meridian. It is 
nearly north and south. 

3. What is this property of the magnet called? 

This property is called the polarity or the directive power 
of the magnet. The term polarity, however, is not restricted 
to this use alone. 



2 MANUAL OF TELEGRAPHY, 

f. What other use has it? 

The possession of opposite forces in the different parts of 
a body of any kind is called polarity. Two opposite forces 
are termed polar forces without reference to the general 
direction of their action. Directive power is but one result 
of polarity in a magnet. 

3, Names of Poles. — 1. What are different poles of a magnet called? 

The end which points northward is called the north pole, 
marked N or ~\- and the other is called the south pole, S or — . 

■I. Are the two poles alike in their effects? 

Either pole of a magnet will take up small pieces of iron, 
in this they are alike. 

3. How do they differ? 

If a second magnet, called an analyser, be presented to a 
needle properly balanced, a new power is soon discovered, 
the power of repulsion. 

1. Descrtlje the experiment iu detail. 

First present N of the analyser to N of the needle; they 
repel each other. Next present S of the analyzer to N of the 
needle; they attract. In like maimer try S of the needle 
with each pole of the analyser. 

4. Z.aw of Magnets.— 1. State the law of attraction and repulsion. 

Poles of the same name repel. Those of op- 
posite name attract each other. 

■2. What is the effect of placing the analyser over the conter of the needle and 
at right angles to it? 

The needle will place itselt parallel to the analyser in every 
case and will stand with its N pole adjacent to S of the 
analyser. 

5. Division of the Magnet.— I. AVhat is the effect of dividing a magnet? 

If a magnet is divided into any number of parts, each part 
will be a perfect magnet, having its tw r o poles and a neutral 
point. 

<i. Magnetics.— l<What are magnetic bodies? 

By magnetic bodies iron and steel only arc meant, as these 
alone are capable of possessing an amount of magnetism 
easily appreciable. 

2. What other bodies can have focLle magnetism? 

Nickel, cobalt, copper and several other bodies are slightly 
susceptible of magnetic influence. 



OF MAGNETISM, 3 

7. Coercive Force — 1. Are iron and steel alike ill their susceptibility? 

Soft iron becomes a magnet readily and loses its power 
instantly. Hard iron is slower both in gaining and losing the 
force. Steel resists with energy and therefore retains its 
magnetism permanently. 

2. What is this resisting poAver of steel called? 

The resistance offered by steel to becoming a magnet or to 
losing its magnetism is called its coercive force. 

3. How can it be overcome? 

The coercive force is diminished by heat or by gentle 
blows with a hammer or by anything which causes motion of 
its atoms, such as filing, grinding and polishing. A white 
heat entirely destroys it. 

-1 Ts coercive force dependent on hardness? 

It is. No iron can be found so soft or pare as to have 
no coercive force at all, and no steel is so hard that it cannot 
be magnetised, or that it will forever retain the force when 
once acquired. 

S. Induction.— 1. What is meant by induction in physics? 

Induction is the awakening or excitation of a polar force 
by its opposite. 

2. Give an example of magnetic induction. 

If one end of a steel bar be rubbed by the N pole of a 
magnet, S magnetism is excited in that end by induction. 

3. Does the rubbing magnet lose any of it3 magnetism by transfer? 
There is no transfer. Magnetism is never imparted but 

always induced. 

4. How arc artificial magnets made,;. 

If a bar is to be magnetized, lay it on a table and bring 
the poles of a U magnet down upon its center with the N of 
the U magnet towards that which is to be the S end of the 
bar, slide the U back and forth on the bar, never beyond 
the ends, then turn the bar over with its ends the same way 
and repeat the process on the other side. Take the U off at 
the center of the bar when the process is complete. 

5. Can induction take place without contact? 

Contact is not necessary to induction, though the nearer 
the bodies are, the stronger and more rapid the inductive 
effort. Friction too assists in the process. 



4 MANUAL OF TELEGRAPHY. 

6. How can 3teel of great coercive force be magnetized? 

If the steel bar be very hard, place it endwise between 
opposite poles of two powerful magnets, heat it by a spirit 
lamp to a dim redness, then suddenly cool it while in that 
position. 

7. "Will a bar of soft iron influence the magnetic needle? 

Soft iron will instantly attract either pole of the needle but 
never repel. 

8. Why does it not repel one of the poles? 

Soft iron held near either pole of the needle becomes itself 
a magnet by induction. The part of the iron nearest that 
pole is necessarily of the opposite name and attracts it. 

9. What proof is there that the soft iron is a magnet while near the needle? 
If a second and weaker needle be brought near the other 

end of the iron, one of its poles will be attracted and the 
other repelled. Also the iron will take up filings at both ends. 

10. How does an unmagnetized steel bar affect the needle V 

Steel at first has but Tittle influence on the needle, but held 
for some minutes near one pole it will feebly attract it, but 
that part of the steel will now repel the other pole. 

11. Why so? 

This is because the magnetism induced in the steel by the 
needle is permanent, as was not the case w r ith soft iron. 

12. Do non-magnetic bodies prevent or hinder induction? 

The interposition of glass, air or other non-magnetic bodies 
between a magnet and a piece of iron does not at all dimin- 
ish the inductive effect 

9. Dia-Magnctics.—l. What are these bodies called? 

These bodies are called dia-magnetics because the magnet- 
ism passes readily through them. More properly they con- 
vey the magnetic influence by a peculiar change in their own 
particles. 

10. Successive Induction.— 1. What is the effect of bringing the opposite 
poles of two magnets together? 

The N pole of one magnet will act inductively on the S 
pole of another in contact with it; the action will be recipro- 
cal and the power of both will be increased. 
2. Is there any limit to this? 

These reactions soon reach their limit as each successive 
induction is more feeble than the preceeding one. 



OF MAGNETISM. 5 

3. Why is a magnet usually bent in the U form? 

The form U favors inductive action between the opposite 
poles of the bar, so that the two will take up a weight con- 
siderably more than twice as heavy as one alone would raise. 

11. Armatures.— 1. How is the magnetism of the U preserved? 

A short bar of soft iron, called a keeper, is placed across 
the ends of the U- This becomes a magnet and by its reac- 
tion keeps up the power of the U magnet. 

2. How can a straight bar be armatnred? 

By surrounding it in any way with masses of soft iron any 
magnet will be kept. 

3. Does hanging a weight to a magnet strengthen it? 

A weight is of no use unless it is of iron and so near as to 
act inductively. The fact of suspension is of no importance. 

4. How is the compass needle kept? 

The compass needle should always be free to^place itself 
in the magnectic meridian when not in use. The earth acts 
upon it by induction precisely as if it were itself a huge mag- 
net. 

12. Astatic Needle.— 1. What is an astatic needle ?J 

A needle, which, though a magnet, has no directive power 
is called astatic. 

2. How can the directive power of a needle be neutralized? 

A bar magnet held over a needle will overcome the earth's 
magnetism thus rendering it astatic. A long needle can have 
its extremities both N while its centre is S or vice versa. 
Such a needle will have no directive power. 

3. Has such a needle polarity? 

It has polarity in the second or general sense, but will not 
point N and S, 

4. What is an astatic system? 

Two parallel needles fastened with brass or wood a little 
distance apart and so suspended that their opposite poles are 
adjacent to each other will constitute an astatic system. 

5. Of what use are they? 

Astatic needles or systems are useful in detecting the pres- 
ence of magnetic forces too feeble to over-come the earth's 
magnetism. 

13. Tfiedries.—l. Why is the intensity of the magnetic force greater at the 
poles than in the center of a magnet? 



MANUAL OF TELEGRAPHY. 

J* All the atoms of a magnet are regarded as 
polarized, that is, each atom is a separate mag- 
net, Fig. 2, and all have their N poles in the 
fig. 2. same direction. At the center both forces 

exist, but at one end northern magnetism is free, and at the 
other southern. Hence at each pole a peculiar force is appar- 
ent. 

2. Do we have at the poles merely the force belonging to one layer of atoms? 
No. From the arrangement of the atomic magnets the 

force is necessarily cumulative towards opposite ends. 

3. Illustrate this? 

SupjDose a bar of iron, suspended by its middle point, to be 
expanded in legth by heat; the expansion is most noticeable 
at the extremities end not at all in the center. At the ends is 
the accumulated motion of all the atoms. 

4. What experiment illnstrates the polarization of the atoms? 

Fill a small thin glass tube with honey in which a great 
number of short bits of iron wire have been stirred; seal it 
and place the tube lengthwise between the opposite poles of 
two powerful magnets. The bits of wire become magnets, 
and turn their N poles all the same way: but the tube will 
as a whole be neutral in the center, and strongly polarized 
at the extremities. 

5. If steel wire were usod in thq experiment would the the tube remain a per- 
manent magnet? 

It would. 

6. On this theory what it the condition' of an unmagnetized bar'? 

In an ordinary piece of iron or steel the two opposite forces 
N and S magnetism are united and neutralized. 

7. What is it to magnetize the bar? 

To magnetize a bar is simply to separate the two magnetic 
forces in each atom, as was done in each bit of wire, and thus 
to polarize the whole mass. 

8. How then do you account for the difference between soft iron and steel? 

Iron is in some sense a eonducto?' of magnetism allowing 
the two forces easily to unite again and neutralize each other 
the moment the inducing agent is withdrawn, while steel 
obstructs the movement. 

9. Does magnetizing a body affect its size or form? 

An iron rod is slightly lengthened on becoming a magnet, 
and it shortens instantly on losing the force. 



OF STATIC ELECTRICITY. 7 

10. Can «a powerful magnet be made by means of a weak one? 
It cannot. In magnetizing a bar the most powerful mag- 
net possible should be selected as induction, even then, is 
never perfect. 



CHAPTER II. 

STATIC ELEOTMOITY. 



1. How docs electricity resemble magnetism? 

Electricity like magnetism includes two polar forces which 
in their unexcited state entirely neutralize each other, giving 
no sign of their presence. 

2. How do they ast whan saparated? 

When separated the two opposite forces powerfully attract 
each other and if not prevented reunite with a violent shock 
attended with light, heat and sound. 

3. What names are given to these opposite forces? 

One force is called positive electricity marked + and the 
other negative or — . Sometimes the first is called vitreous 
and the second resinous electricity. 

4. What is tho origin of the names positive and negative? 

Franklin supposed there was but one kind of electricity. 
Its presence in unusual quantity he called the positive state 
and its absence the negative. This theory is now obsolete 
but the terms are still in use. 

5. How did the other names come in vogue? 

Vitreous or glazed substances were found to yield positive 
electricity and resinous bodies negative. 

2. _E levies.— 1. What are electric bodies'? 

Electricity is not confined like magnetism to a few sub- 
stances, but all bodies are susceptible of it. All bodies are 
therefore properly electrics. 

The term electrics was at first applied to glass, sulphur, 
shell-lac, amber and a few other substances which alone were 
supposed capable of the electric excitement. 

2. Has electricity has any other point of resemblance to magnetism? 

Electricity like magnetism exhibits repulsion as well as 
attraction and each force seems self-repellant. 



8 MANUAL OF TELEGRAPHY. 

3. I.!tw.—1. What is the first law? 

Like electricities repel, and opposite elect- 
ricities attract each other. 

4. Iransferense.—l. la what r3sp3et <U>33 el-33tricifcy especially differ from 
magnetism? 

Unlike magnetism, either kind of electricity may be trans- 
ferred from one body to another, the first apparently losing 
what the second gains. Also a body may have one force to 
the exclusion of the others. 

,7. Separation of the two Electricities. — 1. What if a body polarize! by 
electricity should be divided? 

If the polarized body is cut at the neutral point, one half 
will contain + electricity and the other — . [See section 5.] 

3. Can one force exist without the other? 

Yet one force is always attended by the other in its imme- 
diate vicinity, upon which it reacts. 

4. Can either force be stored up for use? 

Either electricity may be forcibly separated a small dis- 
tance from the other and thus be stored up for experiment. 

5. What is the second law of attraction and repulsion. 

Since electricity attaches itself to certain bodies with some 
force, in its movement it carries the bodies with it. Hence 
the second law, 

Bodies charged with like electricities repel 
each other; those charged with opposite kinds 
attract. 

(5. Why will not one law cover all cas3s? 

The first law explains only inductive action ; the second 
the movement of electrified masses. 

6. Dcvelopn.ent of Electricity by Friction.— 1. How is electricity d3- 
veloped? 

Rub dry warm glass with silk. The electricities will be 
separated by the friction, the positive remaining on the glass 
(which is now said to be excited),, and the negative going to 
the rubber. 

0. How can negative electricity b? captured? 

Rub dry sealing wax or ebonite with flannel. The nega- 
tive remains on the wax and the positive goes to the rubber, 

7. Electroscopes.—! What is an electroscope? 

Any instrument used to detect the presence of electricity 
is an electroscope. 



OF STATIC ELECTRICITY. 



2. Describe the common forms. 
Fig. 3, 




A pith ball suspended from a 
glass support is called a pendu- 
lum electroscope. 

The gold leaf electroscope con- 
sists of two narrow strips of gold 
foil suspended together in a glass 
jar from a metallic rod which 
passes up through the cap and 
terminates in a metallic plate or 
a ball. 



Pith Ball Electroscope. 

8. Experiments.—! What cxperimDut cn-j bs tried with the pith ball elec- 
troscope? 

Hold the excited glass near the pith; three distinct results 
follow: 

First, the glass polarises the pith ball; 

Secondly, it attracts it; 

And, thirdly, it repels it, 

2- Explaiu the first result. 

The glass being positively charged, separates by induction 
the compound electricity residing in the pith, drawing the 
negative to the side next the glass and forcing the positive to 
the opposite side, according to the first law of attraction and 
repulsion. 

3. Explain the second result. 

The glass and pith, having now opposite forces face to face, 
obey the second law and attract each other. 

4. Why do they finally repel each other? 

As soon as the pith strikes the glass its negative electricity 
is neutralized by an equal portion of positive from the glass, 
and having now only positive it is repelled according to the 
second law. 

5. How will the excited wax effect it? 

While the glass repels, the wax attracts it. It will vibrate 
between the two so long as sufficient force remains to 
move it. 



10 



MANUAL OF TELEGRAPHY. 




6. How is the gold leaf electroscope used? 

The gold leaf electroscope exhibits repulsion first, or repul- 
sion alone. 

. Fig. 4. 

The excited glass is held sev- 
eral inches from the knob and 
the gold leaves at once diverge 
When the glass is removed 
they collapse. 

7. Why do they diverge? 
The knob and leaves are polar- 
ised by induction, their negative 
force being drawn to the knob 
and their positive driven to the 
leaves which now having positive 
electricity only, repel each other 
and diverge. 

8. What if th? glass touch the knob? 
Gold Leaf Electroscope. 

It the glass touch the knob a spark will pass. The knob 
and all the metal will now be charged with positive elec- 
tricity by transfer. The leaves will permanently diverge till 
the charge is taken off or neutralized. 

9. Suppose excited sealing-wax be used instead of glass, in these experiment?? 

If wax or ebonite be used the phenomena will be the 
same, though the kind of electricity is precisely the opposite 
in each case. 

9. Sjrfteres of Influence and of Cojntnunicatlon.—l. What is meant by 
the sphere of influence of an electrifled body? 

When any thing is near enough to an electrified body to 
feel its inductive power it is said to be within the sphere of 
influence. 

If it is near enough to receive a spark it is said to be 
within striking distance or within the sphere of communica- 
tion. 

2. How is eacli found? 

The gold leaf electroscope may be used to ascertain approx- 
mately the sphere of influence. But it doubtless extends far 
beyond the point at which any electroscope will move, the 
polarization being more feeble the farther we retreat from 
the excited or charged bod v. 



OF STATIC ELECTRICITY, 11 

10. Conductors,— 1. What are electrical conductors? 

Bodies over which the electrical force passes easily are 
called conductors. Those over which it passes with difficulty, 
or to which it seems to adhere, are called non-conductors or 
insulators. 

2. Illustrate this? 

Suppose a glass cylinder rounded at the ends, to become 
polarized, i. c. to have at one extremity + electricity, and at 
the other — . Notwithstanding their powerful attraction, yet, 
since the glass is a njii-condactor, tli3 two electricities will 
long remain separate, but if the cylinder were of brass or any 
metal they would instantly unite. 

3. What analogy between electricity and magnetism does this reveal? 
The glass seems to have coercive force, called in electricity 

resistance and so retains its polarity like a steel magnet, the 
brass (like a soft iron magnet) offers little resistance to the 
movement of the forces and so instantly loses its polarity 
when left to itself. 

11. Non-Conductors.— -1. What is insulation? 

Insulation is the surrounding of a body with non-conduc- 
tors so that it can neither lose nor receive electiicity. 

2. Are there any perfect insulators? 

No perfect insulators have been discovered, and no perfect 
conductors, and there are all possible degrees between known 
extremes of resistance in different substances. 

3. Give a table of conductors and insulators in the order of their conducting 
powers? 



CONDUCTOU8. 



Metals. 

Charcoal. 

Plumbago. 

Melted salt. 

Water. 

Live or moist flesh. 

Vegetable fibre. 

Oil. 

Spermaceti. 



INSULATORS. 



Ice. 

Glass. 

Dry Fur. 

Silk. 

Diamond. 

India Rubber. 

Ebonite. 

Resins. 

Amber. 

Shell-lac. 

Dry air and Gases. 

The nearer the beg-inning of the list any substance is. the 
better its conducting power. The nearer the end, the better 



12 MANUAL OF TELEGRAPHY. 

its insulating power. Thus ebonite (hard rubber) is a better 
insulator than glass, while shell lac is better than ebonite. 

4. How is the insulating power of g'ass improved? 

Glass varnished with shell-lac is a better insulator, as the 
lac keeps away moisture which is liable to settle on the glass. 

12. Theory of Induction.— 1. How can the electrified body act at a great 
distance from itself! 

Faraday's theory is, that the air, or whatever non-conduc- 
tor intervenes between the electrified body and the object in- 
fluenced is itself polarized in every atom by induction. In 
the figure let C represent the electrified body and A B'the ob- 
6 ject to be influenced; abed 

j> 3 (i (J (1-A. B e *- c '* wm represent atoms of 

13 3 (- MJJ air, the white half of each indp 
3 3 3 3 eating the negative side, and 

the dark the positive side. Through the action of these con- 
tiguous atoms the influence is conveyed to A — B which in 
this manner becomes polarized. 

13. Dielectrics.— 1. What name did he apply to these intervening bodies 
capable of polarization? 

The intervening bodies he named Dielectrics as those con- 
veying magnetic force were called Dia-magnetics. 

2. What bodies convey the force the best? 

Generally the best 7?0;z-conductors are the best //zductors 
or dielectrics, though there are some exceptions. 

3. What experiment shows this exception? 

Let a small disc of brass, instead of the knob, be screwed 
to the top of the gold leaf electroscope, and let another disc 
of equal size be suspended just above and parallel to it- 
Now charge the upper disc very slightly till the leaves 
diverge about an inch. Next push a Cake of shell-lac, with 
an insulating handle, between the disks. Shelldac is a : be**ei j 
insulator than air and the leaves instantly diverge more. 

14. Specific Induction .— 1. What is this power of conveying inductive ef- 
fects called? 

This power is called specific inductive capacity. 

2. Give Harris' table of insulators with the inductive capacity of eochv 
Air - - - - i.oo Beeswax - - - 1.86 

Resin - - - - 1.77 Glass - - - 1.90 

Pitch - - - 1.80 Sulphur - - - 1.93 

Shell lac - - - 1.95 



OF STATIC ELECTRICITY. 



13 



15. Electric Machines.— 1. What are electric Machines? 
An electric machine is any contrivance by which static 
electricity is rapidly produced. 

2. Describe the plate machine? 

The plate machine con- 
sists of a circular glass 
plate turned by a crank 
between rubbers of soft 
leather R which are held 
firmly against it by a 
spring C. A ball N called 
the negative conductor has 
metallic connection with 
the rubber, The plate and 
rubbers are mounted on 
insulating supports. Op- 
posite the rubbers is either 
a brass ball or a cylinder P 
mounted on a glass pillar G 
called the prime conductor 
which is furnished with a row of brass points at W and is 
sometimes surmounted by a wooden ring I, enclosing an 
iron ring. A silk covering S assists in confining the elec- 
tricity to the plate on its passage to the prime conductor. 

3. Taken together what are p and N called? 

The prime conductor and the negative conductor or rubber 
constitute the two poles of the electric machine. 

4. How is the machine prepared for vigorous action? 

The whole machine must be quite dry, warm and free of 
dust. The insulators especially must be carefully kept dry. 
The plate should be clean, and the rubbers smeared next the 
plate with amalgam from the back of a piece of looking- 
glass. A chain should be appended to the rubber and if pos- 
sible have complete metallic commuuication with the earth- 

16. JExp r iments ,--1. What arc some of the effects? 

When the handle is turned, a sharp crackling noise is 
heard, sparks of fire leap along the plate, brushes of flame 
appear at all points and edges and the smell of ozone is 
plainly discernible. 




14 MANUAL OF TELEGRAPHY. 

2. What is its effect on the person? 

If a knuckle be held to the prime conductor a bright 
spark passes accompanied by sound and a prickling sensation. 

3. What is the effect on adjacent bodies? 

The ball of the pendulum electroscope is attracted toward 
the prime conductor, the leaves ot the gold-leaf electroscope 
diverge even if several feet distant. If a brass ball be pre- 
sented a bright, broad spark passes with a loud report. 

17. Intensity and Quantity.— \. Upon what does the s'zc, length and bril- 
liancy of a spark depend? 

They depend upon the intensity and the quantity of elec- 
tricity in the prime conductor and on the size and conducting 
power of the ball. 

2. What is nieaut by intensity? 

Intensity, sometimes called density, relates to the amount 
of force collected on a given surface: for example, two turns 
of the machine will convey twice the intensity to the same 
prime conductor that one will. This ratio will be maintained 
till the prime conductor has all it can retain. 

3. What governs quantity? 

Quantity with a given intensity depends on the size of the 
prime conductor. A prime conductor of one hundred feet 
surface will, with the same intensity, contain twice as much as 
one having but fifty feet. 

4. How is this illustrated by heat? 

A red-hot knitting-needle has the same intensity of heat 
as a red-hot poker, but a much smaller quantity. Again, a 
large stove, at low temperature, will warm a room as much 
as a small stove red-hot. Here the quantity in the source of 
heat may be the same but the intensity different. 

5. Give corresponding examples in electricity. 

A cloud, miles in extent, may be feebly charged while the 
quantity in the aggregate is enormous. On the other hand, 
the largest machines give but small quantity as compared 
with a cloud, but exhibit the highest intensity. 

18. Tension.— 1. What is electric tension? 

Tension is the tendency to leap from a charged surface. 
It depends upon the intensity but must not be confounded 
with it. The tension increases much faster than the intensity. 
Laplace teaches that tension increases as the square of the 
intensity. 



OF STATIC ELECTRICITY. 15 

1'J. The MacFtius Polarised.— 1. In what state is ths machine when in ac- 

t ion ? 

Iii action and just afterwards, ths machine is polarized the 
positive electricity remaining on the prime conductor and 
the negative on the rubber and its connections. 

20. Discharge.— 1. What is it to discharge the machine? 

To discharge the midline is to restore the equilibrium by 
allowing the + and — electricities of the prime conductor 
and rubber to reunite. 

2. What are the methods of discharger 

There are three modes of discharging the much ine called 
the conductive the convectivz and the disruptive discharges. 

3. Describe the lirst. 

Suppose both poles of the machine to be insulated: 
i. Before the handle is turned, connect the rubber with the 
prime conductor by a wire or chain. Then on operating the 
machine the separated electricities silently reunite over the 
path thus provided, forming a feeble electric current. This 
is the conductive discharge. 

4. Give the seoond mode? 

If the machine after turning is allowed to stand awhile, the 
particles of air near each conductor become charged with 
the opposite forces, and by their motions finally produce 
equilibrium. This is the convcctivc discharge. 

3. II jw may this movement of the air be perceived? 

The movement of the charged particles of air as they are 
repelled from the machine may be felt on the face or hand 
held near either conductor. Sharp points directed toward 
the machine or attached to it greatly favor this discharge. 

G. The third mode. 

' Let one end of a chain or wire be fastened to the rubber 
and the other to a brass ball which has a glass handle; bring 
the ball within striking distance of the prime conductor. The 
forces now unite with an explosion. This is called the dis- 
ruptive discharge. 

21. Connection ivit'i the Ground .— I. What is the effect of conaeetiug the 
rub'jer with the ground? 

By far the most important practical effect is to form part 



16 MANUAL OF TELEGRAPHY. 

of a circuit, from the rubber around through the earth , toward 
the prime conductor. So that the operator standing on the 
floor, which also has connection more or less perfect with 
the earth, can complete the circuit at will, and get a free dis- 
charge from the prime conductor. 

2. How does it place every uninsulated body? 

Every uninsulated body is thus placed in direct co?i?iection 
with the rubber or negative pole of the machine. 

3. Is the chain uwaUy attached to the rubber? 

It is always assumed that the'ehain is to connect the rub 
ber with the earth, unless the contrary is indicated. 

4. Can th3 same effect bo obtained ia any other way? 

This effect can be obtained by covering the floor, where the 
experiments are tried with metal, which communicates with 
the rubber. 

5. Does the rubber retain its negtivc charge in that case? 

If the rubber is nearer the prime conductor than any other 

part of the conducting medium, it shows decided polarity. 

•Otherwise the negative electricity is drawn away from the 

rubber to that point of the uncompleted circuit which is nearest 

the prime conductor. 

22 Limited Charge— 1. Why is the charge limited when both rubber and 
prime conductor are insulated? 

The charge at either pole is not limited in supply, it is sim- 
ply held fast by the mutual attraction which the two forces 
have for each other. Let a path be made between them as 
described for the disruptive discharge and the supply seems 
unlimited except by the size and power of the machine. 

23, Free Flectricity.—l. Is not the electricity of the prime conductor more 
free when the rubber is uninsulated? 

The positive electricity is no more free to go back to the 
rubber /, c. to meet the negative in one case than in the other. 
It is more free to take a circuitous route through other bodies, 
and through the earth, and that is all that can be meant by the 
term free. 

24. Itaito of Inensity and Quantity.— 1, Can a very large prime conduc- 
tor be charged as well when both polesbf the machine are insulated? 

A large prime conductor can be as well charged as a small 
one, provided the insulation is perfect, and the negative con* 
ductor is of equal size with the positive. 



OF STATIC ELECTRICITY. 17 

2. W'l'al ii' it is not of equal size? 

The quantity of the negative and positive forces being 
equal, if the negative conductor is small and insulated, its 
charge soon reaches so high a tension that disruptive dis- 
charge over the glass follows. The intensity of the two con- 
ductors is in the inverse ratio of their surfaces. 

2o Enlarging one of the Conductors.— 1 What then is the second effect of 
connecting the rubber with the earth? 

Connecting the rubber with the earth is the same as mak- 
ing the negative conductor as large as the earth. Its inten- 
sity will therefore be as much less than that of the prime con- 
ductor as the surface of the prime conductor is less than that 
of the earth, or practically zero. 

•J. lias the rubber then no polarity when co. nected with the earth? 

If the rubber is nearer the prime conductor than any other 
conducting medium, which communicates with the earth, it 
is still somewhat polarized by induction from the prime con- 
ductor. 

26. Diversion Of Inductive Influence.— 1. How is it that we can obtain 
! mall sparks from cither conductor when both are insulated? 

Though the mutual attraction is strong between the two 
conductors, yet a third body brought quite near either will 
share the inductive influence and become polarized and may 
exchange electricities with it to a small extent. 

27. Permanent Charge.— 1 How can a permanent charge be imparted to a 
body? 

A permanent, positive charge may then be obtained, if the 
rubber is uninsulated, by first insulating the body and then 
connecting it with the prime conductor.. This in effect makes 
it a part of the prime conductor. It may afterwards be sep- 
arated from it but will retain the charge. 

2. How can thu negative charge be secured? 

Connect the prime conductor with the earth and attach 
the insulated body to the negative conductor. It will become 
negatively charged when the plate revolves. 

28. Effect of Insulation— 1. What force binds a charge to the surf ace of 
anything? 

The charge remains on any thing for want of a conductor 
to allow it to escape. The better the non-conductor that sur- 
rounds it the more firmly is it held. 



18 



MANUAL OF TELEGRAPHY. 



2. What was the old theory? 

It has been taught that atmospheric pressure holds the 
charge, but Faraday's theory of dielectrics (sec. 25, Chap. 2$ 
makes this extremely improbable if not impossible. 

3. Why then is it that a charge of higher intensity may be given in condensed 
than in rarlfled air? 

Rarefied air becomes more easily polarized and is a better 
conductor than dense air. 

39. Distribution of Charge.— 1. Is the intensity of a charge everywhere 
alike? 

If the prime conductor is a sphere the intensity is uniform; 
if a cylinder, with rounded ends, the intensity is greatest at 
the extremities and nearly neutral in the middle. The force 
will accumulate on every projection. 

2. Does the charge reside on the outside or does it pervade all the atoms of a 
body? 

It manifest^ itself on the surface only. A hollow cylinder 
will receive as high a charge as a solid one. 

3. What experiment proves this? 

A sphere covered with hemispherical cups with glass 
handles loses all its electricity if the cups are removed. 

Fig. 7 





1. Is there any exceptions to this? 

Where the intensity is great and long continued especially 
on the surface of poor conductors the charge will penetrate 
and the cups must be used more than once to remove it. 

30. Insulating Stool.— 1 What is the apparatus for chargirgthc human 
body? 

An insulating stool having glass or ebonite legs is provided 
on which a person may stand and take hold of a chain 
attached to one of the conductors. 

31. Experiments.— 1 What amusing experiments are made? 



OF STATIC ELECTRICITY. 



19 




A person thus charged may with his finger set the to ether 
or to benzine or to powdered resin; can light the gas, fire a 
hydrogen pistol or communicate a shock to others. His hair 
if dry and free, will stand erect. 

2. Expsrimaats with other apparatus? 
Fig. 8 

Amongst other things bells are rung; im- 
ages are caused to dance or swing; a mimic 
I hail storm is produced by suspending a plate 
of brass within a glass jar, over small pieces 
of paper or pith, which have been scattered 
on the metallic floor of the jar. 

3'2. Variety of Machines.— 1 What other electric 
machines are in use beside the plate machine? 

The Cylinder machine, the Hydro elec- 
tric machine and the Holtz machine are in 
common use. 

2. Describe the cylinder machine? 

The cylinder machine has a glass cylinder 
instead of a glass plate, which is turned by 
a crank against a silk rubber. 

3. What is the hydro-electric machine? 
Mimic Hailstorm. 

A small steam boiler is mounted on glass legs and the 
steam issuing from narrow wooden pipes, generates large 
quantities of electricity by the friction thus produced. 

4. What is the Holtz machine? 

The Holtz machine, so called from the name of its inven- 
tor, consists mainly of cwo thin circular plates of glass, one of 
which revolves with great rapidity very close to the other 
which is stationary. The stationary plate is charged nega- 
tively at one or two points by striking it with cats fur. The 
revolving plate is charged by induction from the stationary 
one and its electricity may be taken off by means of a row of 
points, as in the other machines. It is extremely effective, 
furnishing electricity in great quantities, and high tension 
without friction. 






33. Elect rophorous. What is the Electrophorous? 



20 



MANUAL OF TELEGRAPHY. 
Fig. 9 




Elcctrophorous. 



The electrophoresis consists ot a 

cake of resin, shell-lac or ebonite, 

cast in a shallow plate of tin or 

iron E, and a movable tin cover T 

./Which has a glass handle G. 

3. How i> itcharge:!? 

If the cover is removed and the 
resin struck a few times with cat's 
fur or flannel, the cake will be 
charged with negative electricity. 
The cover on being replaced be- 
comes charged, by induction, with positive electricity on its 
lower side and with negative on its upper side. If we touch 
the finger to the upper side to let the negative escape, we 
may immediately after lift up the cover by its insulating 
handle, and it will be charged with positive electricity and 
will yield a spark. 

3. Does this discharge the eake? 

This does not discharge the cake but the process may be 
repeated an indefinite number oi times. 

4. Why does not the second contact of the cover discharge the resin? 

Perfect contact no doubt w T ould; but the contact is slight 
and at few points. The cake is a non-conductor and the ten- 
sion is extremely feeble. 

34. Flectric Condensation.— 1 How can the charge of the prime conductor 
he intensified? 

Let two insulated plates of metal be placed a few inches 
apart facing each other and let wires connect one with the 
prime conductor the other with the rubber. The intensity 
of the two plates will be much higher than could be given to 
either of the conductors. 

2. Why is this? 

It practically brings the two poles of the machine nearer 
together causing two results. 

ist. Successive inductions arise analogous to the reactions 
of two magnets, which greatly increase the intensity. 

2d. The polar forces by their mutual attraction capture or 
disguise or practically neutralize each other, so that neither 



OF STATIC ELECTRICITY. 



21 



Will leave its plate or manifest its pressure by the electro- 
scope. 

3. What is the common form of this experiment? 

The common method is to insulate the first plate and con- 
nect the second with the ground. The first will then receive 
repeated charges from the prime conductor. 

4. How can this intensity be farther greatly increased? 

Let now a pane of glass take the place of the air as an insu- 
lator between the plates, and we can bring them much nearer 
together without a discharge. The glass in no wise hinders 
inductive action while effectually holding separate the two 
poles. 

.". In what casa would induction be the greatest possible? 

If the glass were infinitely thin and yet strong the induc- 
tion would be perfect. As it is, extreme intensity can be 
given till the disruptive discharge takes place shattering the 
glass. 

35. IiCydcn Jar.— 1. What is the best form of this apparatus? 

The Leyden jar is the most convenient apparatus made on 
this principle. It is a glass jar, coated inside and out, except 
a few inches at the top, with tin-foil. It is stopped with a 
varnished wood cap, through which passes a stout wire to 
the inner coating. At the top of the wire is a brass knob. 

2. How is the jar charged? 



Fig. 1 




It is charged by holding it 
in the hand with the knob to 
the prime conductor. The 
hand furnishes a path for 
positive electricity driven 
off from the outer coating, 
and for the return of nega- 
tive from the rubber, or the 

Charging the Leyden Jar? eal *■"■ 

3. JTow do avc know that any positive electricity is driven off? 
The presence of positive electricity on the inner coating of 

the jar makes it necessary according to the first law of attrac- 
tion and repulsion, but a confirmation of the fact is afforded 
by the cascade series. 




22 



MANUAL OF TELEGRAPHY. 




36. Cacccde Stries.—l. Describe the experiment in detail? 

Fig. 11. . . , r 

A scries of Ley- 

den jars is so ar- 
ranged on insu- 
lating stands that 
the knob of each 
successive one 
shall communi- 
cate with the outer coating of the one before it. The last of 
the series is uninsulated. Charge the first and remove the 
jars by means of the insulating stands and all will he found 
charged alike. 

2. How is this explained ? 

Each knob, after the first jar, is positively charged from the 
outer coating of its predecessor, giving up its negative in 
exchange, and leaving each jar rjolarized. The last of the 

series receives its negative from the rubber through the 
ground. 

37. Quantify in a Chnrtffd ,Jar.—l. 
cleetrieitv than one not charged? 



Doc? a charged jar contain more 



A charged jar has no more electricitv than when neutral. 
It has merely substituted negative for what positive it had 
in its outer coating and positive for the negative of its inner 
coating. 

2. What then is the true condition of a chargedjjar ? 

A charged jar is simply polarized, the two coatings being 
in opposite and equal states of intensity-. 

3. What modification of this stat£ment should be made? 

In the common way of charging the jar, the connection ot 
the outer coating with the rubber is imperfect, and the thick- 
ness of the glass prevents perfect induction, so that when the 
charge is finished there is usually in the interior, a slight ex- 
cess of the positive electricity. If the connections arc equally 
good there is no difference whatever. 

4. Can this excess be thrown into the outer coating ? 

If the jar is held by the knob and the outer coating be pre- 
sented to the prime conductor the jar will be charged nega- 
tively, and a positive excess will be found in the outer coat- 
ing. All this is reversed if the prime conductor is uninsu- 
lated and the charge is taken from the negative pole. 



OF STATIC ELECTRICITY. 23 

SS. Discharge hy Instalments. -A. If Hie charged jar be insulated, will the 
knob yield a spark? 

When there is an excess it will yield it, of course, and if it is 
perfectly polarized and a good conductor is brought nearer the 
knob than the coatings are to each other, a relation is established 
exactly like that between the coatings, only less extensive, and 
a slight discharge takes place leaving a small excess in the 
outer coating. The outer coating will then yield a spark, 
reducing its intensity a little below that of the interior and so 
on. 

2. Why cannot the. -first spark be taken from the outer coating? 

If the jar stands on an insulator while being charged hav- 
ing metallic connections with the poles of the machine for 
both coatings, the first spark may be taken from either coat- 
ing. But handlhio the jar, as in the usual mode of charging, 
always leaves the excess in the inner coating. The thinner 
the glass the less is this excess. 

39. Triple Coating Jar.—l. How is fcho relation (allu lei to in See. 33; of a 
third body to the inner coating shown? 

Let a jar of ebonite in the form of a large tumbler, be turned 
to the uniform thickness of the eighth of an inch and provi- 
ded with accurately fitting, movable coatings. Let now a 
second jar, exactly fitting this on the outside, be made half as 
thick and coated only on its outer surface. Charge the first 
jar in the usual way and place it inside the second, on an 
insulator; connect the innermost and outermost coating. The 
+ electricity will leave the innermost coating and come out- 
side so as to be nearer the middle or — coating. We may 
now remove the inner jar with its interior coating, the outer 
jar will remain charged. 

2. What does this experiment prove? 

This proves that the electricity of either coating is free to 
leave it provided it is thus brought nearer its opposite force. 
The knob is a small portion of the inner coating. The knuckle 
or other conductor brought very near it is like part of a 
third coating. 

40. Automatic Discharge.— 1. What apparatus exhibits the discharge by 
instalments? 

Between two bells which are connected with the outer 



24 



MANUAL OF TELEGRAPHY. 



Fig. 12. 




and inner coating a small brass 
ball is suspended by a silken 
fibre. The ball will vibrate 
till the jar is discharged. 

2. la what other way is Hi is per- 
formed? 

A modification of this ex 
periment is often made by 
charging one jar from the 
prime conductor and another 
from the negative conductor, 
a ball will vibrate between 
the knobs till they arc dis- 
charged. 



Automatic Discharge. 



41. Charging an Insulal.d tTur.—l. Can an insulate! jar be chirked? 

An insulated jar can receive but a feeble charge, there 
being no path for the escape of positive electricity from the 
outer coating, or the return of negative from the rubber. 
The inner coating of such a jar would be merely an exten- 
sion of the prime conductor. 

4?. Discharge of The J~ai'.—1. How is the jar discharged? 

A wire fork terminating in brass knobs and havinsr a glass 
or ebonite handle is used to make metallic connections 
between the coatings without exposing the operator to the 
effects of the shock. 

2. How may the shock be taken? 

If one wishes a shock he has but to place one hand against 
the outer coating and touch the knob with the other. 

43. Electric Bubbler!/.— 1. What is an e'.ectdc batter}? 

A battery consists of any number of Leyden jars, standing 
on tin-foil and having their knobs connected by a wire. For 
convenience, they are usually placed in a box, from one side 
of which a knob extends, which has connection with the 
external coatings. 

44. Use of the Coatings.— -1. Of what use are the coatings of the jar? 
The coatings are the first to be polarized when the jar is 

ch?rged, and they spread the charge instantly over the sur- 
face of the glass. Without such a conducting medium the 



OE STATIC ELECTRICITY. 



25 




glass could only be charged slowly and irregularly in differ- 
ent parts. 

2. Does the charge reside in the coating? 

The coatings merely conduct the electricity. If a jar has 
movable coatings they may be severally removed but the 
electricity remains on the glass. 

45. Polarization of th<i Glass — 1. In what condition is the glass then? 

Glass being a dielectric its atoms are polarized as repre- 
sented in the figure. The distance I repre- Fi s- 13 - 
sents the thickness of the glass, I the inner 
coating and the outer. The particles next 
the inner coating are positively charged and * 
those next to negatively, while the interven- 
ing particles arc simply polarized. 

46. Residual Charge.— 1. What is the residual charge? 

A second discharge may be obtained if the jar has stocd 
charged any considerable time, because the charge has pene- 
trated the glass to other layers beyond those nearest the coat- 
ings and is slow in coming to the metallic surface. 

47. Disguised Electricity.— 1. What name is given to the polarized forces of 
the jar which do not affect the electroscope? 

All the electricity of the jar, except the slight excess which 
has been referred to, is called disguised electricity; because, 
like the compound force, it does not affect the electroscope. 
Actually combined forces are only more effectually disguised. 

2. Is disguised electricity found only in jars or other condensing apparatus? 

It is found to a certain extent in the two conductors of the 
electric machine when both are insulated, and in general 
whenever two bodies charged with opposite forces arc near 
enough together to act inductively on each other. 

47. Spontaneous Discharge— 1. Does a ja; ever discharge itself sponta- 
neously ? 

The disruptive discharge frequently occurs over the glass, 
from the upper edge of one coating to the other. An intense 
charge always tends to creep up the glass. If the jar is thin 
the disruptive discharge often takes place through the glass, 
destroying the jar. The silent conductive discharge is accom- 
plished when the glass is moist. The air will in time silently 
accomplish the convective discharge, though a hermetically 
sealed jar will sometimes retain a charge for months. 



2 6 MANUAL OF TELEGRAPHY, 

49. Electric LtgJit.-l What causes the lightof tha spark? 

The light is due to two causes, ist. The air is intensely 
heated, and 2d, There are incandescent particles of the charged 
bodies in the path of the spark. 

•2. How isthe latter fact shown? 

If the knob of the jar be plated with silver, and that of the 
discharging rods with gold, the gold surface, after the dis- 
charge, is studded with silver particles, and the silver one with 
gold. After a discharge between substances easily pulver- 
ized, the air in the vicinity is filled with fine dust. 

50. Electric Force— 1, Is there any force in the movement of these atoms? 

These atoms move with sufficient force in the discharge of 
the Leyden jar to perforate thick card board. 

•2. To what is the destructive effect of lightning due' 

It is not certain whether the instantaneous polarizing or 
neutralizing of atoms is in itself destructive. The destructive 
effect of lightning is due in part at least, to the infinitely rapid 
transportation of particles of water, air, wood or earth, and 
in part to the sudden expansion caused by heat. 

o l. Elcalrie Sound.— 1. What'causes the sound which accompanies electric 
discharges? 

The sound is due to the collapse of the air after the pass- 
age of the electrified matter through it. When lightning- 
strikes," the rending of bodies of wood, rock etc, adds to the 
sharpness and loudness of the report. 

2. What causes the rolling sound of thunder? 

The rolling of thunder is due to the reflection of the sound 
from cloud to cloud and between the earth and clouds. 

o?. Lightning Rods— On what principle are lightning rods constructs -.? 

On the principle that sharp points receive or discharge 
electricitv with great facility and in silence. 

'2. How is this shown? 

Let a bundle of narrow strips of tissue paper, fastened 
together at one end, be supported b\' a thick wire upon the 
prime conductor to represent a cloud. By their self-repell- 
ancy the strips, when charged, will stand as far apart as pos- 
sible. If a sharp point be directed toward them, even at the 
distance of five or six feet, they at once collapse. A ball will 



OF STATIC ELECTRICITY. 2 7 

have ilo effect till brought within as many inches. 

53. Effect of Points.— 1. Illustrate a discharge from a point. 

A wire terminating in a point projecting from the prime 
conductor will effectually prevent the accumulation ot a 
charge. 

2. How is this accounted for? 

This is a necessary consequence of the self-repellancy of 
electricity. Let two spheres of different size on glass sup- 
ports be charged to the same intensity. If now they are 
made to touch each other, the lesser sphere will instantly 
exhibit higher tension than the larger. A series of spheres 
diminishing in size to a point will show so great an accumu- 
lation of the force toward the smallest that the air can no 
longer resist the tension and the whole is dissipated. 

54. Moitrs of J^fottucitif/ Electricity.— 1. Is there any other war of excit- 
ing electricity than by friction or induction? 

There are several others, each giving nam 2 to a distinct 
branch of the science. 

2. Mention the different branches by their uanics. 

i. Frictional Electricity excited by Friction. 

2. Voltaic " ' : ' : Chemical Action. 

3. Thermo- " " " Heat. 

4. Magneto- " " " Magnetism. 

5. Animal " " " Animal Organs. 

t>r>. Static Elsairtstty.-Whzt is Siatie Electricity? 

In whatever manner it is excited, electricity may be made 
to abide on a surface instead of flowing alon^ a wire. When 
thus captured it is termed Statie (stationary) Electricity and 
is treated as a distinct branch of the subject? 

50. DynaniicZElectricity — 1. What is Dynamic Electricity? 

When electricity moves along a wire or other conductor 
in the manner of a current it is called Dynamic (forceful) 
Electricity. 

2. With which is the electric telegraph chiefly concerned? 
The telegraph makes use of dynamic electricity in its ordi- 
nary operations, though static electricity is often a great dis- 
turbing force in the way of the telegraph. In ocean cables 
static electricity is a very important agent. 



28 



MANUAL OF TELEGRAPHY. 



CHAPTER III. 

VOLTAIC ELECTRICITY. 



/. V<i!tn. -1. \\ hsi; is tho origin of tho term Yoltate? 

This tomi is derived from Vclla, the nam; of the Italian 
professor who invented (A. D. iSdd) what is known as the 
voltaic battery. 

2. Ths Battery, -D^zvibz the battery. 

A cell or element of such a battery is a glass jar nearly filled 
with acidulated water, in which is placed a plate of copper, 
C, and another of zinc, Z, each plate 
terminating in a copper wire soldered to 
its dry end. A number of such elements 
connected forms a battery. 

2. What arc tli3 carls of Jho wire r alio I? 
The free ends of the wires are termed 

Bfc^ the positive and negative poles or often 
Rthe + and — electrodes. 

3. What is tho battery circuit? 

Voltaic cell. The circuit consists of the zinc, the 

fluid, the copper and the wire; forming together a conducting 
path for the electricity. 

4. What is it to close and break tho circuit':' 

To close the circuit is to join the wires. Separating them 
again is called breaking or opening the circui t. 

5. How long arc the terminal wires? 

The wires may be of any length, even to hundreds of 
miles, provided a sufficient number of cells be used. 

G. What names are given to the plates"? 

The plates are named from the electric condition of their 

dry ends. Thus the copper is called the positive plate and 

the zinc the negative plate. 

NOTE. — This is given in accordance with the, practice of telegraphers 
though usually in treatises on physics the opposite names are used. 




OF VOLTAIC ELECTRICITY, 



29 



3. Electric Coalitions.— 1. Whal 

the circuit? 



'.i. 1 cnllti >:i ol tin plat33 before clos- 



Fig. 15. 



As soon as the plates are set in the liquid they become pol- 
arized; the dry end of the zinc being — and the wet end -f-; 
the copper the reverse. 

?. WhaS is tlij'proDf of this polarization? 
If the electrodes are soldered to 
a disc of metal and the two discs 
placed facing each other like con- 
densers, they exhibit xery decided 
electric tension. 



l 



K\ 



I 



: 3 c 8 



J 



cP S^ 



l + 



?. What is the condition of the liquid atoms? 
The liquid atoms arc likewise pol- 
arized. Water is a compound of 
two parts of hydrogen gas to one 
of oxygen. Each group of three small circles in the figure 
represents a single atom of water; the oxygen black, the 
hydrogen white. The lower line of circles exhibits the 
polarization of the atoms of water, each presenting its oxy- 
gen or -jr side toward the zinc and its hydrogen or — side to 
the copper. 

1. Closlny Ch-c:tii — 1. What is th^cXjst of closing the circuit,; 

The electrical effect is to set in motion a current of elec- 
tricity from the zinc to the copper in the water and from the 
copper over die wire to the zinc in the air. 

2. What is the chemical effect? 

The chemical result is illustrated by the upper line of atoms 
in the figure. The oxygen nearest the zinc lets go its hydro- 
gen, which released, moves to the next group in the direction 
of the copper plate, takes its oxygen to form a new atom of 
water and sends its hydrogen onward. This process of dis- 
solving and forming water croes through the line till the 
hydrogen reaches the copper where it is set free. 

3. What becomes of (he sulphur of theacul? 

Oxygen, zinc and water unite with a portion of the sul- 
phur to form sulphate of zinc — which is held in solution. 

i>. Tlit- Car-rent.— 1. In what sense is the word current employe;!? 

Strictly speaking the current is but an infinite number of 
feeble discharges of electricitv in constant succession. These 
infinitesimal discharges arc taking place all over the we* 



30 MANUAL OF TELEGRAPHY. 

portion of the zinc and the electricity is carried with the 
hydrogen to the copper. 

2. Is there a'.so a negative current? 

There is an equal number of discharges of negative elec- 
tricity from the wet surface of the copper, carried along 
with the oxygen to the zinc and over the wire back to the 
copper. 

3. Which is meant by the current? 

When the current is spoken of the positive current is 
always intended, unless the word negative or the — sign 
accompanies it. 

(i. Inconstancy of tit: Battery.— 1. Whai becomes of the free hydrogen? 

A part of the hydrogen rises and escapes into the air. A 
part forms a film of minute bubbles all over the immersed 
part of the positive plate. 

2. What effect has this? 

This rapidly reduces the power of the battery and renders 
its action unreliable. 

3. Is there any way to prevent this? 

Smee's battery, modeled after Volta's, employs, instead ot 
copper, a plate of silver coated with platinum black which 
roughens the surface and quite prevents the film. 

4. Describe Smee's battery? 

F.g. 16. The silver plate is placed between and very 
near two zinc plates. The three plates are sus- 
pended on a bar of varnished wood extended 
across the top of the jar. The zinc plates are con- 
nected at the top and furnished with a binding 
screw for the wire, as is also the silver. 

7. Local Action.— 1. Does any hydrogen arise from the zijic? 

Nearly all zinc is impure, particles of lead, iron 
Smee's battery, or other metals being mixed with it. Thus in all 
batteries small electric currents are set in motion on the sur- 
face of the zinc itself causing hydrogen to escape in great 
quantities. 

2. How is this prevented? 

If the zinc is first cleansed in dilute sulphuric acid and then 
dipped in mercury part of the zinc surface is dissolved and 
flows over all the impurities. 




OF VOLTAIC ELECTRICITY, 



31 



3. What i» this process called? _ 

This is called amalgamating th<* zinc audit must always 

be performed thoroughly with every kind of battery. 

8. Two Fluid BattcHcs.-l. Why arc two fluid batteries used? . 

Daniell, Grove and others have made use of different fluids 

around the two metals in order to consume the hydrogen 

o-as and render the battery constant. 

o 

•2. Describe the Darnell's battery? 

Danieli's battery has, first, the outer glass cell or jar, next, 
a copper cylinder open at one side and the ends, inside that 
a porous earthen cup, and in the cup a star shaped rod of 
zinc. 

3. What are the liquids? 

Xext the zinc is sulphate of zinc and next the copper is a 
saturated solution of sulphate of copper. 

4. What is the object of the porous cup? 

The liquids must be kept separate, and yet a moist connec- 
tion must be maintained between the metals or the current 
would be cut oft'. 

5. How is the saturation of the liquids maintained? 

Sulphate of zinc is constantly formed inside the porous cup 
by the action of the battery. The sulphate of copper, how- 
ever, is constantly precipitating its pure copper and send- 
ing its sulphur through the porous wall. It must, therefore, 
be supplied with crystals of the sulphate, kept constantly in 
a copper basket, in the outer jar. 

6. How does Daniell's compare with Grove's battery? 

Grove's battery is equally intense with this, and will -sup- 
ply several wires as readily as Daniell's will one. 

7. Describe Grove's battery? 
Grove's battery has the usual glass jar 

containing a mixture of eight parts of wa- 
ter and one of sulphuric acid. In this is a 
zinc cylinder open at the side and ends to 
admit' freely the acid. Within the zinc 
cylinder stands a small porous cup filled 
even with the outer liquid, with strong- 
nitric acid. In the nitric acid is a slip of 
platinum which is the positive plate. The 



Firr. 17. 




MANUAL OF TELEGRAPHY. 




zinc has an arm carrying the binding screw for the negative 
electrode, and which also, in case of a single cell, sustains by 
an insulated support the platinum plate and screw. 

">. What is the chemical process? 

The strong nitric acid consumes the hydrogen eras giving 
off nitrous oxide fumes, which are offensive and poisonous. 
Bichromate potash mixed [ with the acid aids in keeping down 
the fumes. 

S. What is Bucsen's battery? 

Bunsen's battery is like Grove's except 
than Bunsen uses a bar of carbon in place 
of the platinum. His cells are often of great 
size and a fluid called electropoion is substi- 
tuted for nitric acid. 
9. Why is this fluid hotter? 

This gives off no fumes, is cheaper, and 
is nearly as effective. 

13. What is its composition? 

One gallon of sulphuric acid is mixed 
with three gallons of water. In a separate 
vessel live or six lbs. bi-chromate of pot- 
> r v. ash should be dissolved in two gallons of 
boiling water and thoroughly mixed with the other. 

0. Quantity in Voltaic Electi'lcift/.—l. In what respect does Voltaic elec- 
tricity differ from Frictional? 

The electricities are the same in kind. Bat eleetricity fur- 
nished by chemical action is of low intensity and of great 
quantity. 

XOTE. Bj mzans, hereafter explained, Voltaic ehctricity may be 
stored up, or bcioraz strtic, so as to exhibit as high intensity as that pro- 
duced by friction. 

■?.. What results from thisjlifference of intensity? 

Because of its feeble intensity Voltaic electricity will tra- 
verse many miles of wire rather than pass over the hundreth 
of an inch of clear space or through a thin covering of silk or 
of varnish. 

3. Illus'.rat: the quantity obtained from a Grove ce i? 

Faraday found that to decompose a grain of water required 
three and three-fourths minutes with a Grove element. 
While to do the same by frictional electricity requires the 
charge of a Leyden battery having a metallic surface of thirty- 
two acres. 



OF VOLTAIC ELECTRICITY. 



33 



4. What determines the quantity? 

The size of the cells determines the quantity other things 
being equal. 

10. Quantity and Intensity Batteries.— 1. What is a quantity battery? 

Where great quantity is desired the zincs of different cells 
are connected together as one, and the positive plates are 
also joined. The effect is the same as increasing the size or 
cells. 

3. What is an intensity battery? 

If intensity is sought, each zinc is connected with the pos- 
itive plate of the adjoining cell, the wires being attached to 
the zinc at one end of the series and to the positive plate at 

the other. 

Fig. 19. 




Intensity Battery. Grove. 

3. What is the comparative strength and intensity of such batteries: 

A battery of two cells, with the zincs joined as one, lu.s 
only the intensity of one with the quantity of two. The 
same battery, with the zinc of one connected to the platinum 
of the other, has quantity one, intensity two. 

4. What effects require great intensity? 

An intensity current will go a greater distance, overcome 
greater resistance, or leap across a wider space. 

5. What is accomplished by quantity? 

Chemical effects, heating, lighting and magnetizing power 
depends more upon quantity; though both intensity and 
quantity contribute to these results. 



34 MANUAL OF TELEGRAPHY. 



CHAPTER IV. 

ELECTRO-MAGNETISM. 




1. The Magnet.— 1. What is an electro -magnet? 

Fi s- 20 - A bar of iron subjected to the influ- 

S ence of a voltaic current becomes polar- 
ized by induction and is hence called an 
electro-magnet. 

2. The Melix.—l. How is the current applied? 

The wire from the battery is coiled 
Electro -Magnet. spirally around the bar so that the cur- 

rent in passing over the wire moves at right angles to the 
bar. 

2. Does the wire touch the bar? 

No. The wire is insulated by being covered with silk and 
varnish, and the opening may be larger than the bar, though 
the nearer the wire is to it the more powerful the induction. 

3. What is this apparatus called? 

The coil of wire with or without the bar is called a helix. 
If the spiral turns from left over to right, as in the figure, it 
is a right-handed helix. If it turns in the opposite direction 
it is a left-handed helix. 

3. Relation of Poles to the Current.— 1. What determines the direction of 
the poles of the electro-magnet? 

The direction of the pole depends upon the direction of the 
current. In the figure the current enters the helix near S. 

2. What is the rule? 

The south pole will always be at the end where the current 
ejiters if the helix is right-handed. The reverse is true if the 
helix is left-handed. 
8* 



OF ELECTRO-MAGNETISM, 



35 



4. The Solenoid. 



-1, What is a solenoid? 
Fig. 21. 




This word 
means a tubu- 
lar magnet. It 
is technically 
applied to a he- 
lix whose ends 
* are bent back 
through the 
coil to the mid- 
dle, where they 
emerge with- 
The Solenoid. out contact in 

any part. Two such are seen in the annexed figure. 

2. Why is it called a magnet? 

Such a helix is found to possess all the properties of a mag- 
net. If one solenoid be delicately suspended, as in the figure, 
it will stand in the magnetic meridian, and if another be used 
as an analyzer it will alternately attract or repel it precisely 
as a magnet will act on a needle, [p. 2.) 

3. How will the solenoid affect a bar placed within it? 

A bar placed in the solenoid becomes a magnet whose 
poles are the same as those of the solenoid itself. 

4. What may be used as an analyzer of the solenoid? 

A steel magnet may take the place of either solenoid, and 
will exhibit the same result. 

5. Ampere's Theory.— 1. State Ampere's two postulates? 

A helix traversed by the current is a magnet, the positions 
of whose poles depend on the direction of the current. Con- 
versely, a magnet may be conceived to owe its properties to 
currents of electricity which traverse it. 

2. What is Ampere's theory of magnetism? 

Ampere's theory is that the atoms of magnetic bodies are 
continuously traversed by currents of electricity in different 
directions; that to magnetize a body is simply to place these 
currents parallel to each other. When all are parallel the 
magnet is saturated. 

3. How does the solenoid explain this? 



3 6 MANUAL OF TELEGRAPHY 

Flg * 22, The single current 

of the solenoid is 



^MMi-w&r*-*'*" 



ryy* infinitesimal parallel 
currents. 

4. How do the currents at the poles differ? 

If the currents were visible, on looking at the N end of a* 
magnet they would be seen moving from right over to left. 
And if the magnet were also transparent one could look 
down the length of it and all the currents would be seen to 
move in the same way. But on inverting it and looking at 
the S end the currents appear to move from left over to right 
as in the figure. 

5. On this theory why do opposite poles attract each other? 

The currents of opposite poles when placed together move 
in the same direction, as if the two magnets were but the 
continuation of one magnet. Like poles repel because their 
currents oppose each other. 

6. Permanency of Electro -may nets. —I. How long will tho electro-magnet 
retain its force? 

Mr. Elisha Gray's experiments have shown that a pure soft 
iron bar may be magnetized and demagnetized many thous- 
and times in a second. 

2. What is Gray's exporimont? 

He uses a tuning fork, to one leg of which a fine platinum 
spring is soldered, to open and close the circuit. To the end 
of the electro-magnet a thin plate of metal is screwed. The 
vibrations of this plate will correspond to the number of times 
the iron is magnetized and demagnetized. They are proved 
to be as rapid as those of the tuning fork by the identity in 
pitch of the sound produced. 

3. Can permanent magnets he made hy the current? 

If there is any hardness about the iron from hammering, fil- 
ing etc., a residual magnetism is developed. And if a steel 
bar be introduced into the helix, a permanent magnet results. 

4. What if the bar is bent or too large for the helix? 

To magnetize a steel U place it end to end with the poles 
of a U electro-magnet, move a piece of soft iron back and 
forth along the steel never beyond the bend. Take it off at 



OF ELECTRO-MAGNETISM. 



37 




the center. Turn the system over 
without separating and operate 
^ as before. Open the circuit be- 
fore removing the steel. 

7. Power of the Electro-magnet.— 
1. What apparatus exhibits the power of the electro-magnet? 

A thick ring of soft iron is cut into semi* 

circular halves and a small helix is made 

to fit loosely on one of them. A current 

through the helix will cause the halves to 

adhere with great force. 




Ring and Helix. 
8. Form.—l. What form is favorable for strength? 




In general the U form is best. 



An 



arrangement like that in the figure will 



sustain hundreds of pounds. 

For many purposes two spools or 

bobbins of iron wound with insulated 

wire, and screwed fast to a straight 

+ piece of iron at one end is the best 

form. 

9. Electro Motors.— 1. Define electromotors. 
Electro-Magnet. Com Form. An engine driven by the force of an 
electro-magnet is called an electromotor. 
2. Why are not such machines in common use? 

The expense of this force is many times that of steam, 
though it is more compact. A small fraction only of the 
actual force generated has ever yet been utilized. 

10. Practical JJses.—l. What is; the most important application of the 
fjree? 

The value which far transcends all others in importance is 
found in its applicability to the electric telegraph. 

2. What minor uses may be mentioned? 

It is also employed for burglar and fire alarms, hotel annun- 
ciators, the recording of minutes and exact dates of astronom- 
ical or other events; nearly all of these are modifications of 
the telegraph. 

11. Deflection of the Needle— 1. What was Oersted's discovery? 
Oersted, in 1S19, discovered that a voltaic current passing 

northward over a magnetic needle will cause its N pole to 



38 



MANUAL OF TELEGRAPHY. 



turn west. If it pass northward under the needle the N pole 
will turn east. 

2. What is the law of the movement? 

Ampere gave the following- rule to aid the memory; 

Suppose a metallic human figure be made a part of the cir- 
cuit, and so placed that the current shall enter at his teet and 
leave by his head, then if his face be always toward the needle 
the N pole will be deflected toward his left. 

3. What if the current go northward over the needle and return under it'? 

Passing the current around the needle in the direction of 
its length doubles its power of deflecting the needle. 

4. Is there any limit to this mode of increasing the power? 

The power increases with the number of convolutions of 
the wire, but diminishes with its distance from the core. 

12. Th° Galvanometer. — 1. What app'ieatiDn is made of this principle?. 

This principle is 
used in the construc- 
tion of the galvanom- 
eter,an instrument for 
detecting and meas- 
uring very feeble cur- 
rents. 

2. Descri se it. 
An astatic system 
(Sec. 12; question 5; 
chap. I,) is suspend- 
ed by a very fine plat- 
inum wire is a glass 
(case. A flat helix of 
pbnnany convolutions of 
H the finest insulated 
igcopper wire is sup- 
~-\JT^^~ ~ : ~~ v^-ported on a wooden 
^ ';—_ -■: /^ _ ■—-"-" or ebonite frame so 

^ ~The Galvanometer. that the lower needle. 

is enclosed within it and can turn freely. A card under the 
upper needle is graduated to show the amount of motion. 
The wires of the helix terminate in the binding screws. The 
instrument is provided with leveling screws and the helix 




OF INDUCED CURRENTS. 



3 9 



may be turned so as to place its wires parallel to any position 
of the needle. 

3. What are some of the uses to which it is applied? 

The special use of the galvanometer is to reveal the pres- 
ence of a feeble current and to measure its force. It may be 
employed to detect an escape or waste. The receiving instru 
ment of the ocean telegraph is a modified form of the galva- 
nometer. 



CHAPTER V. 

iztTiDTTaiEiD ott:r,:r,:e:n-ts- 



1. ^Electro Magnetism.— 1. What has already been observed respecting the 1 
helix? 

We have seen (Sec. 4 Chapter IV) that the helix itself pos- 
sesses the properties of a magnet, having polarity and the 
power of repulsion as well as attraction. 

2. What is now proposed? 

We are now with the galvanometer, to compare the helix 
and magnet still further and identify their characteristics 
more fully. 

3. What was Faraday's reasoning? 

"If electric currents," said Faraday, "induce magnetism 
then magnetism should induce currents, 
this true. 



Experiment proves 



4. Describe the experiment': 
Fig. 2 7. 




Currents from a Magnet. 



Let a helix, with or with- 
out a soft iron core, have its 
terminal wires screwed into 
the binding posts of a galva- 
nometer. Next let one pole 
of a steel magnet move to 
and from the end of the he- 
lix as in Fig. 27. During 
this motion the needle of the 
galvanometer will vibrate. 

5. What is the direction of this 
U current? 

While the magnet is ap- 
proaching, the current will 



40 



MANUAL OF TELEGRAPHY. 



have the same direction as the Amperean currents of the mag- 
net. When the magnet recedes the current is reversed. 

6. What if tk3 magnet is held still? 

When the motion ceases the current ceases, however near 
the magnet may be to the helix. The more rapid the motion 
the stronger the current. 

7. What is the effect of suddenly reversing the poles of the magnet? 

- Reversing the magnet will cause an equally sudden rever* 
sal of the current, as this implies the receding and approach 
of each pole alternately. 

8. What machine is constructed on this principle? 

In Clark's magneto-elec- 

trio machine this sudden re- 
versal is affected by causing 
two helices with their cores 
to revolve in front of a per- 
manent horse-shoe magnet of 
great power. The change of 
polarity in the core cause*? a 
succession of induced cur- 
rents in the helices. By means 
of a commutator E S, Fig. 28, 
the currents are made finally 
to flow in a single direction. 

0. What is the essential point in 
~ _ ~' : TlaTk's MaVhine! tnc production of induced currents? 

The essential condition of producing the currents is the 
constantly Varying intensity of inductive influence. 

10. How is this accounted for? 

There is here no infinite succession of electric discharges 
such as the dissolution of zinc in a battery furnishes. The 
induced current so called is but a single wave of polarization 
that traverses the wire and ceases. But every movement 
which brings the magnet neaier, by increasing the amount of 
polarization starts a new wave. Withdrawing the magnet 
releases the tension and allows the return wave of neutraliza- 
tion. 

2. Primary and Secondary Currents— 1. What are secondary currents? 

A current is called secondary when it is induced in an insu- 
lated wire by another current called its primary. 




OF ELECTRO-MAGNETISM. 



41 



2. What is the arrangement of the wires'? 

The apparatus for secondary currents is exactly the same 
as for electro-magnetic currents except that a small helix con- 
nected with a Bunsen element takes the place of a magnet, 
as in Fig. 29, P is the primary helix and I the secondary. 

Fig. 29. 




3. What is characteristic of this current? 

The secondary current is far more intense than the primary 
but depends for its existence on a constant movement of the 
primary helix, or else a constancy varying power of the bat- 
tery. 

4. What arrangement will give a strong secondary current? 

Let the primary helix be placed inside the secondary fitting 
as closely as is consistent with the best insulation, and let a 
core of soft iron be inserted in the primary helix. As this 
precludes any movement of the primary 3 variation of battery 
intensity is employed instead. 

5. How is the greatest possible variation secured? 

Rapidly opening and closing the circuit is of course the 
extreme of variation and gives the most intense secondaiy 
currents. It is accomplished by drawing one electrode 
quickly along a coarse file. 

(>. What is the direction and duration cf the secondary current? 

The secondary current thus produced is an instantaneous 
shock or wave merely. Its direction as shown by the gal- 
vanometer is the reverse of the primary at the instant of 
closing the circuit and the same as the primary on opening- 



42 



MANUAL OF TELEGRAPHY. 



3. Currents of the Third and Higher Order,— 1. What are the currents of 
the third order? 

The secondary current, notwithstanding its brief duration, 

is capable of inducing a third current in a helix near it, and 

this a fourth and so on. Currents as high as the ninth order 

have been made. 

4. The Extra Current. -1. What is the extra current? 

While the primary wave is traversing one part of a helix it 
excites an induced current in the adjacent parts of the same 
helix; these are called extra currents to distinguish them 
from currents which require a second helix. 

5. The Induetorlum. — 1. What is tlie Inductorium? 

This is a compact arrangement of powerful helices for ren- 
dering the electricity of the induced current static and of as 
high intensity as that of the best friction machines. 

2. What are the dif- 
ferent parts of the ap- 
paratus? 

An inner pri- 
mary helix, P, of 
coarse copper 
w i r e two or 
three layers deep 
surrounds a core 
of soft iron par- 
allel wires, M. A 
glass or ebon- 
=' ite spool I sur- 
The inductorium. rounds the pri- 

mary coil, containing in Ritchie's coils, from live to eighty 
miles of the finest copper, insulated wire. The basement is 
filled with many square feet of tin foil between insulating 
sheets of oiled silk. 

3. What is the use of the tin foil layers? 

These have the effect of absorbing the extra current which 
is a disturbing force. 

4. At what points does the electricity appear? 

The terminals of the outer helix are the electrodes of the 
secondary current. These maybe connected with handles as 
in the figure, or employed in any way to give direction to 
the discharge. 




THE ELECTRIC TELEGRAPH. 43 

5. How large a battery is required? 

With a secondary helix of fifteen miles of wire and a bat- 
tery of eight Bunsen cells most beautiful and brilliant effects 
are produced. 

6. How is the circuit opened and closed? 

The interruption of the current is often made by a toothed 
wheel turned by a small crank against a break-piece. 

In the figure an automatic interrupter is seen at B. The 
current on its way to the primary helix operates a small elec- 
tro-magnet; this draws down an armature and breaks the 
circuit. A spring closes it again as soon as B ceases to be a 
magnet. 

7. What caution is to be observed? 

The shock of such a charge would be serious if not fatal. 
A Leyden jar is fully charged with a single break of the 
circuit. 



CHAPTER VI. 
ELECTRIC TIELIEG-^R^IPIH:. 



1 . What is a telegraph ? 

Any instrument by which ideas are directly transmitted a 
great distance is a telegraph, [tele far, grafiho to write.) 

2. What are the old forms? 

Thus signal fires, rockets, colored lights, bells and guns, 
and sometimes figures and words, to be read by telescopes 
have long been in use. 

The army and navy signals are extremely ingenious and 
must continue in use at sea. 

3. What is peculiar to these methods? 

In all these the operator makes only large movements in his 
own neighborhood, to be seen or heard by a distant observer. 

4. How are they limited? 

They are limited to comparatively short distances and few 
expressions. 

5. What power does the electro-magnet furnish? 

The electro-magnet furnishes that essential requisite of a 
complete telegraph, the power to move matter which is far 
fro?n the operator at will, in at least two directions. 



44 MANUAL OF TELEGRAPHY. 

6. What advantage docs this give to the electric telegraph" 
This enables us to construct an instrument which shall 
express every shade of thought at any distance, over every 
variety of surface and at all seasons, and yet occupy but an 
inappreciable time in the transmission. 

1. History.— 1. With whom did the idea originate? 

It is not known who first suggested the idea. It was 
entertained as soon as electricity became a science. 

2. What were the practical measures adopted for its us3? 

1740. Franklin invented the cylinder machine for fric* 

tional electricity. He sent a wave two miles and killed 

an animal. 
1747. Bishop Watson, of London, sent a signal two miles, at 

Shooters hill, using the Ley den jar. 
1753. Sir Francis Roland published his system. He sent 

messages S miles using synchronous revolving dials with 

letters on them, and pith ball electroscopes. 
1774. Lesage, at Geneva, erected a telegraph with twenty- 

four wires, one for each letter. The signal was a lettered 

pith ball. 

1519. Oersted discovered the power of the current to deflect 
the needle. 

1520. Ampere proposed to letter twenty-four needles and 
move each by a separate voltaic current; the first use of 
chemical electricity for this purpose. 

1833. Weber and Gauss, of Prussia, simplified this by using 
fewer wires and needles. 

1S34. Professor Henry, of Washington, sent messages three 
miles using the armature of an electro-magnet to give the 
signals. 

1S37. Prof. Morse procured his patent for the Morse alpha- 
bet and register. 
In the same year Steinheil, in Germany, and Wheatestone 

and Cooke, in England, took out patents for their systems, 

still in use, but rapidly giving place to Morse's system. 

£. The Telephone. 

In 1073 Elisha Gray, of Chicago, substituted for the ordi- 
nary vibrator of a small inductive coil, a slip of steel so thin as 



THE ELECTRIC TELEGRAPH. 45 

to give a clear musical tone, his object being to transmit the 
vibration over the wires of the secondary helix and reproduce 
the tone at a distant station. The success of his experiment 
was complete. By inserting the common telegraph key in 
the primary coil the duration of this musical tone could be 
controlled at pleasure. The receiving instrument at first was 
a thin plate of German silver attached to a ground wire and 
stretched across the bridge of a violin to increase its sonor- 
ous qualities. The operator at the receiving end took the line 
wire in one hand and moved the fingers of the other gently 
over the plate, when a clear sweet note came out, of the same 
pitch as the steel vibrator at the other end. It was found 
that animal tissues were thus perfectly responsive to the 
vibrations. 

Mr. Gray soon after made use of the primary current alone, 
producing the necessary interruptions by vibrating springs. 
For a receiver he substituted a single long helix with a core 
of soft iron, to one end of which was screwed fast the sound- 
ing plate. A soft iron rod lengthens every time it becomes 
a magnet, and shortens again when the circuit opens. In 
this way the plate is shaken and the tone comes out. A 
recent improvement in the transmitter is made by using the 
key to strike a tuning fork to which a delicate platinum 
spring is s:>ldere_l. Tills sp;ing is the interrupter. Letting 
up the key damps or stops the vibrations of the fork. The 
present receiver is a fine steel ribbon stretched like a bow 
string across a small frame and placed like the armature of 
an electro-magnet, only not near enough to touch. The rib- 
bon is tuned to the pitch of the transmitting fork and responds 
clearly and beautifully to the attractions and repulsions of the 
magnet. 

On Mr. Gray's recent visit to Europe the invention was 
thoroughly examined and approved by Prof. Tyndall and 
others of the highest authority, as it had already been in this 
country. It was found to operate through the Atlantic Cable 
with the same facility as over land. 

The commercial value of this invention lies in the fact that 
by branching the line wire at the ends, any number of trans 



46 



MANUAL OF TELEGRAPHY. 



nutters and receivers can operate over the same line, each 
beinsj on a different pitch and not interfering with the others. 

By combining the transmitters with a single instrument 
melodies and even harmonies may be sent as easilv as a sin- 
gle note. Mr. Gray received tunes in Washington which 
were transmitted from Chicago. This instrument seems des- 
tined to work an entire revolution in telegraphy as it multi- 
plies the capacity of tvery wire and every cable many fold. 
It may also possibly lead to a marked simplification of the 
telegraphic alphabet. The sustained tone renders possible 
the use of rythmical symbols so that a single movement may 
stand for a number of different letters, and no letter need 
have more than two characters. 

3. Jlorse Electric Telegraph.— 1. What is the Morse Telegraijhic sys'.em? 

The Morse system permanently records a message by 
the power of the electro-magnet on a narrow strip of paper. 
The Morse alphabet (see frontispiece) being constructed to 
require only dots and straight maiks. 
2. Describe the key. 



Fig. 31. 




The Morse key con" 
sists of a brass lever A 
B about five inches long 
A hung upon a steel arbor 
between set screws. 
The lever is connected 
with one electrode of the 
battery. It is capable 
of vertical motion only 
F F through a very small 

space. An ebonite button at A is used to depress the lever 
till it strikes the small platinum anvil, which is the opposite 
electrode, and insulated from the frame. This closes the cir- 
cuit. A spring raises it when the pressure is withdrawn thus 
opening the circuit. When the key is not in use, the circuit 
closer is pushed against the anvil. The screws F F fasten 
the key to the table. 
3. Describe the register. 
An electro-magnet M is placed near one end with terminal 



THE ELECTRIC TELEGRAPH 



47 




48 



MANUAL OF TELEGRAPHY. 



wires attached to binding screws at A. Above the electro- 
magnet is the armature C which carries a lever having a 
small vertical motion between set screws at B. The other end 
of the lever carries a steel point P. A strip of paper is carried 
over the steel point and between two grooved rollers by clock 
work. The clock is propelled by weights attached to the 
drum D. 

4. What is the operation of the register? 

When the circuit is closed by the distant operator the 
armature is attracted by the magnet M and the style P is 
pressed against the paper. The groove allows a slight line 
to be thus embossed upon the moving paper, its length being 
at the will of the operator. 

5. What is the relay magnet? 

As the current on a line of more than 20 or 30 miles be- 
comes too feeble to work the register, it is passed through a 
pair of helices called a relay magnet whose office it is to open 
and close the circuit of a local battery at the receiving station. 
The local battery operates the register. 



6. What is its construction? 
Fig. 33. 




It is made of very 
fine wire (30 to 36) 
very long and very 
closely wound. The 
armature in front of 
the helices carries an 
upright lever. One 
Relay Magnet. electrode of the local 

battery enters this lever, the other, after passing the register 
enters the frame F which has a platinum point at P. When 
the armature is attracted the local circuit is closed. A spring 
withdraws the armature when the line current is broken. 
Fig. 34. 7. what is the sounder? Xhe sounder is an instru- 

ment for reading a message 
by the ear. It is an electro- 
magnet with armature and 
Clever like the register but 
without the recording ap- 
paratus. This in many cas- 
?Bfa es supercedes the necesity 
fjl of a register or of a local 
: battery. A current too fee- 







THE ELECTRIC TELEGRAPH. 49 

ble to work the register is often ample for the lighter move- 
ment of the sounder. 

- 8. What is the box sounder? 

The box sounder is designed to give resonance to the sound 
of the lever. Its construction is like that of a relay except 
that the magnet is enclosed in a fine mahogany case. It is 
used principally as a main-line sounder, and also as a relay. 

Fig. 35. 




Box Sounder, or Relay. 
9. Describe the pocket relay. 

In the pocket relay the lever is brought down so as to pack 
It is a main-line sounder and is used by line 



m a case 
repairers. 



Fig. 36. 



rocket Relay, 
10. What is the switch: 



The switch, or commutator is a contrivance for quickly 
changing the current and for coupling or dividing circuits. 

4 



50 



MANUAL OFTELEGRAPHY. 



11. Describe the ground switch? 



Fig. 37. 




Ground Switch. 
and C. 



The ground switch has a lever A at- 
tached to a wire leading to the earth. 
Two studs B and C connect with the 
line wire on either side of the instru- 
ments. By means of an ebonite button 
the lever A may be used to connect 
eithei line with (he ground. 

12. The button switch? 

In the button switch the ground wire 
is wanting nnd the lever mav unite B 



Fig SS. 




Fjci.S9. 




The Ting Switch. The Plug. 

The plug switch is a stout brass spring placed firmly against 
a stationary pin whose pressure is regulated by a set-screw A. 
The binding screws at the top of the figure connect with the 
main -line. 

The wedge or plug consist of twopieces of brass insulated 
from each other by bone rubber, and furnished with avulcan- 
ite handle, as shown in fig. 39, which shows it of actual size 



THE ELECTRIC TELEGRAPH 



51 



The wnes leading to the relay are attached to this plug and 
firmly held by binding screws. 

When the plug is inserted on the switch, as represented in 
fig. 38, the main current is diverted through the relay, but it 
cannot be interrupted or "broken" by inserting or withdrawing 
the wedge; in the latter instance the spring instantly closes 
the circuit when the wedge is withdrawn. 

14. What is the Culgan switch? 

The Culgan switch is designed for offices which many lines 
enter. Straps of brass A B C D E E, Fig. 40, are placed vertical- 
ly on a varnished plank, or other non-conductor, and furnished 
with binding screws at the top for the line wires. Rows of 
short buttons with ebonite handles hang between the straps 
and have metallic connection with the binding screws, I, II, 
III, IV, V, VI, VII, at the side. The upright straps are all 
cut in two in the line x x* and joined again by pushing a 
brass peg between the ends. One is seen withdrawn at X. 

It may be seen by a slight inspection that any of the upper 
binding screws as A can be connected with any of those at 
the side as V by turning the appropriate button. 

15. How mauy wires would the board in the figure accommodate? 



B 



Fig. 40. 



D E 




The Culgan Switch. 

E, C and F being opposite electrodes. 



At a way station 
a switch with srx 
straps and seven 
horizontal wires 
would provide for 
three through lines 
ail three i nst ru- 
in ments. 

VS. Wh.it would b3 
IV the method? 

Suppose th re e 
wires from the east 
b~Kfl vt terminate in the 
binding screws A, 
vn B, C, and three 
from the west in P, 
E,F:Aand D.Bai d 






52 



MANUAL OF TELEGRAPHY. 



Let instrument No. i, be connected with the side srews I 
and II; Inst. No. 2 with III and IV; and No. 3 with V and 
VI. The ground wire is at VII. 

If we wish the lines, whose electrodes are A and D to be 
shunted through instrument No. 1, turn the buttons so as to 
connect A with I and D with II. 

If the line is to go through direct, without shunting, sim- 
ply connect A and D to the same horizontal wire. 

17. For how mari5' wires at a terminal station would this provide? 

This switch would provide for six wires at a terminal sta- 
tion. 

It is obvious that any line may be shunted through a loop 
as well as through an instrument by the same arrangement 
and the switch board may be of any size. 

18. What is the lightning arrester? 

The danger of injury to instruments and operators from 
lightning, has led to the device called the arrester. As static 
electricity prefers a short route over a poor conductor to a 
long one over a good conductor, it can easily be diverted 
from the offices as follows: 

Fi &- 41 - A plate of brass five or 

six inches long is attached 

to the ground wire. On 

this is a sheet of varnished 

silk and above the silk 

other plates of brass at- 

1 ': tached to the line wires. 

li PPi 1 '"' 1 ' '' I ' ' IPS Th e lightning easily passes 

Arrester. into the lower plate and 

thus to the ground, while the voltaic current will not go 

through the silk. 

19. Describe Bradley's arrester? 

Bradley substitutes air for the varnished silk and has sharp 
points attached to each plate reaching nearly over to the 
other plate. This is a very effective instrument and is used 
also for a srround or a shunting switch. 

20. What are repeaters? 

When the distance from the sending to the receiving office 
is great the current does not go through, but is employed at 




THE ELECTRIC TELEGRAPH. 53 

way stations to open and close the circuit of a second battery 
which continues the message to a third and so on without 
rewriting. The apparatus for this is called a repeater. It is 
nearly the same in form as a relay or sounder. 

21. How far may messages be sent by this means? 

There is no practical limit to the distance. Messages have 
been sent from Harvard Coll. to San Francisco and back to 
the same office with the view of ascertaining the speed of 
transmission. The distance in this case, reckoning the length 
of wire in the repeater as well as in the line wire, was up- 
wards of ten thousand miles which occupied about seven- 
tenths of a second. 

22. For what other purpose is the repeater u*ed? 

The repeater is valuable for transmitting news simultane- 
ously over different branch lines. 



64 MANUAL OF TELEGRAPHY. 



PART SECOND. 

PRACTICAL TIEI.fEa-R/A.IPIHlY. 
CHAPTER I. 



THE BATTERY. 



Note. Attention is given in this chapter to the four forms most in use 
the Daniell, the Grove, the Bunsen and the Callaud batteries; the latter, 
a. modification of DanielVs, is rapidly coming into favor. 

1, The care of JSa teries.—l. Why does the lottery first claim attention? 

As the battery is the source of power it is of the highest 
importance that every thing pertaining to it be kept in most 
perfect working order. A filthy, wet, or leaky battery rs not 
only extremely untidy' but extremely wasteful and danger- 
ous to health. It is also an excellent test of the general thor- 
oughness and trustworthiness of the operator. 

2. Daniell s Battery.— 1. How is "Darnell's battery set up? 

If the battery is to be used at once, dilute sulphate of zinc 
should be used for the porous cup and a perfectly saturated 
solution of sulphate of copper in the jar. The zinc is to be 
amalgamated and inserted in the porous cup. The liquids 
may then be poured in till thev are at the same level and the 
jar nearly full. 

2. "What attention do the connections need? 

The connections are to be filed bright and all dust removed. 
Sand paper or emery are apt to leave non-conducting parti- 
cles on the metals and are to be discarded. Connect the 
zinc of one cell to the copper of the next through the battery. 
The current always starts from the copper. 

3. The bine vitriol? 

The sulphate of copper is continually disappearing and 
when it is gone the current stops, also sulphate of zinc comes 
through the porous cup. The perforated cup or basket 
attached to the copper must always be supplied with pulver- 
ized vitriol. 



OF PRACTICAL TELEGRAPHY. 56 

4. Care of the sulphate of zinc? 

The action of the battery produces sulphate of zinc and 
when the solution in the porous cup is overcharged it crys- 
tallizes on the zinc and destroys the current. Part of it 
should occasionally bo taken from the porous cup and its place 
supplied with water. 

5. How often do the zincs need cleaning? 

Once in two weeks the zincs should be taken out scraped 
and cleaned with a stiff brush, and amalgamated. Save a 
third of the clear part of the liquid to return to the porous 
cup, fill up with water. 

(j. Care ol* the porous crip? 

The porous cup is to be thoroughly washed. See that no 
cracked cup is replaced, as it occasions great waste of power. 
To prevent as much as possible the copper deposite let the 
zinc not touch the cup. The copper deposite is not to be 
wasted when the cups are used up. 

7. How are the copper cylinders kept? 

The coppers should be cleaned of all deposites once in 
three months. They will probably last a year. 

8. Care of the jars? 

New r jars unless they are of glass should be saturated with 
paraffme. The edges must be wiped with a damp cloth to 
remove crystals, otherwise insulation is destroyed by moist- 
ure between the jars and great waste of "power results. All 
dirt and rust and moisture must be kept away from the floor 
on which the jars rest. When the jars are moved dry wood 
ashes should be used to clean the shelf or floor where they 
stood. 

!•. What docs the Callaud Battery require? 

The Callaud battery dispenses with the porous cup while still 
using two fluids. It is constructed on the principle that sul- 
phate of copper is heavier than sulphate of zinc. 
10. How are the metals placed? 

The copper, with its sulphate and a good supply of crystal 
in powder, is placed at the bottom of the glass cell. The 
zinc in form of a wheel lies at the top of the fluid immersed 
in sulphate of zinc and supported by a frame across the top 
of the jar. A gutta-percha-covered wire leads up from the 
copper to furnish the positive electrode. 



56 MANUAL OF TELEGRAPHY. 

II. What other battery is similar? 

Hill's battery differs from this only in the shape of the 
metals. These are much used in telegraphy. 

These batteries must be placed where there is the least ftos- 
sidle jar as any disturbance mixes the liquids and destroys 
the power of the battery. 

3. Care of the Grove batterrt/.—l. How is the Grove battery set iri? 

For long use, set the tumblers in position, and fill them half 
full of the solution. One part of sulphuric acid to twenty- 
five of water by measure, thoroughly mixed. 

Next set in the zincs to which the platinum strips are sol- 
dered, with arms to one side of the line of cells. 

Place the porous cup inside the zincs and fill them with 
strong nitric acid to the level of the top of the zincs. Lastly 
turn the arms and immerse the platinum strips in the acid. 

2. What if several wires are worked by one battery? 

If four or six wires are worked the sulphuric acid should 
be in a little greater proportion say one part to twenty of 
water. A single wire is worked by one to thirty. 

3. How often is it renewed? 

A Grove battery in constant use should be taken down 
every night, the nitric acid put away in stoppered bottles and 
the zincs placed inverted in acidulated water. In the morn- 
ing the zincs are rubbed with a brush and, unless bright like 
silver, moistened with a few drops of mercury which is rub- 
bed evenly over them inside and out. 

4. How often are the acids renewed? 

Add one part in ten of nitric acid every morning. Renew 
the sulphuric acid entirely once a week. 

5. How long will such a battery last? 

The platinum strips last till they are broken up by careless 
handling. The zincs dissolve or become perforated and 
worthless in about three months. 

A warm situation promotes dryness as well as chemical 
activity. 

4. The Carbon 7JaM«*7/.— (see page 32.) 1. What caution is to be observed 
in setting up a Carbon battery? 

As carbon is a poor conductor of electricity extra care 

should be used to have a broad surface contact with the metal 



OF PRACTICAL TELEGRAPHY. 



5? 




and to have the clamps screwed up. The zincs require the 
same treatment as for the Grove battery. New zincs must 
be thoroughly amalgamated a second time after three days 
use. 

2. How of ten does the battery need cleaning? 
Fi s-^ This battery 

needs to be tak- 
en apart once 
in two weeks, 
when the zincs 
should be brush 
ed and amal- 
gamated and 
the carbon soak 

ed in clear wa- 
Carbon ±sattery. 

ter. Take care that no green rust is left between the carbon 

and its metal. 

3. Which battery is most useful? 

When several lines are to be worked bv one battery, 
Grove's is far the most effective, working twice as many 
wires as the Carbon battery. Yet it is no more intense. Fifty 
Grove cells will send the current no farther'that fifty Bunsen 
cells. 

4. Which is mo>l expr-asivo? 

The whole expense of purchasing and running the Grove 
battery is more than three times that of the Bunsen battery. 
It is cheaper, therefore to supply tzvo sets of the latter, each 
working three lines, than to have o/?cofthe Grove battery 
working six lines. 

5. How often does the electropoin fluid need ronewal? 

One third of the fluid in the porous cup if the battery is ill 
constant use, needs to be withdrawn, by means of an ebonite 
pump or syringe, every day, and its place supplied with new. 

8. The zincs? 

The zincs with proper care last a year and sometimes a 
year and a quarter. 

7. Should the jars of a battery bo insulated from each other? 

It is absolutely essential to insulate all the jars f}'ow each 



68 MANUAL OF TELEGRAPHY. 

other and from the ground. Glass jars if kept dry insulate 
themselves. Dry stone* ware jars saturated with parafine 
need no further insulation. Ordinary stone- ware jars con- 
tinually exude moisture and must have separate insulation. 
A small plate of crockery ware inverted over a hlock an inch 
thick makes an excellent insulating support. A glass plate 
with perpendicular rim is the best. 



CHAPTER II. 

CARE of insrsTi^xj^/EEisrTS. 



4. The Key.— I. What direction* are given Tor the key? 

ist. The connections must be kept perfect, else leakage 
and loss result. 

2d. When the key is not in use the circuit is always to be 
closed, otherwise the line is inoperative bevond the station 
where the carelessness occurs. 

3d. Examine occasionllv the platinum points of the anvil 
and lever to see that no corrosion or dirt injures their perfect 
contact. 

4th. Wipe off all moisture or dirt about the circuit closer 
which might cause partial connection when the circuit is 
open and make the key stick. 

3. The Relay. 1. What directions for the relaj ? 

ist. Examine the platinum points, as for the key, and 
remove corrosion with a very fine file used carefully, for plat- 
inum is worth more than its weight in gold. 

2d. If the relay is unsteady or confused adjust the springs 
of the armature bv means cf its thumb-screw. 



CARE OF ^INSTRUMENTS, 
Fig. 43. 



59 




Relay. 

In many instruments the adjustment is made by moving 
the cores of the magnet as in the figure. 

3d. In rainy or very changeable weather it is necessary 
to attend to this adjustment with the nicest care and obser- 
vation, separating the cores from the armature, or the oppo- 
site, to make sure whether the line is in use by other offices. 

4th. The key should never be opened till this point is set- 
tled. 

5. T'<\e Sounder— 1. What care does the sounder require? 



Fig. 44. 



1st. Adjust the 
spring of the sounder 
lever so that the back 
stroke shall be lighter 
than the direct stroke, 
caused by closing the 
circuit. 

2d. If the local 
sounder docs not ope- 



■ — " does, the fault must be 
Jjocal Sounder. 

in the local circuit. Ail the local connections must then be 
examined till the cause of the mischief is discovered. 

.7. The Register.— Ho what defects is the action of the register liable? 

1st. The paper may run crooked. This can be remedied by 
adjusting the pressure on the upper roller. The pressure on 
the two ends must be equal. 

2d. The paper may stick in the guides. This is probably 




60 MANUAL OF TELEGRAPHY. 

the fault of the paper, which is not cut of uniform width. If 
the guides are adjustable separate them slightly. Otherwise 
remove the paper and put in new. 

3d. The armaturemay stick. This happens when the arm- 
ature is allowed to touch the cores of the electro-magnet. It 
is remedied by adjusting screws at the end of the lever. The 
lever should have barely motion enough to let the style clear 
the paper and go into the grove without scratching against 
the roller. 

4th. The marks made by the style may be indistinct or of 
bad shape. See that the pivot screws arc adjusted as to give 
the lever no side play and that the style stands exactly oppo- 
site the grove. 

6. Thp Arrester.— 1. To what injuries is the lightning arrester su jeet? 

i si. The common form of arrester is liable to dampness 
between the plates as paper is often used instead of varnished 
silk. It should be often taken apart and examined to pre- 
vent serious escapes of the current from this cause. 

2d. A discharge of lightning: through the arrester will 
often carbonize the paper or silk, thus rendering it a conduc- 
tor; or ma}" even fuse the plates together, making a perfect 
escape for the voltaic current. It should never be left with- 
out inspection after a storm. 

Bradley's arrester, manufactured by L. G. Tillotson <fc Co. 
Xew York, is subject to neither of these mischances. 

7. The Repeater.— 1. What care does the repeater need? 

1st. The same cautions that apply to the relay are applica- 
ble also to the repeater. 

2d. Beside this, it is to be remembered that as it takes time 
for the repeater lever to move, the duration of the current 
sent on by it, is shorter than that which it has received. The 
lever should therefore have the least motion that will answer 

2. What caution is necessary in using repeaters! 

In sending a message through repeaters, especially it there 
are several, more time than usual should be allowed for con- 
tact by the key, both in making dots and dashes, and a^ much 
less time for spaces, 



TELEGRAPHIC MANIPULATION, 61 



CHAPTER III. 

TELEGRAPHIC MANIPULATION 



J, Management of the Key.—l. What hints are given for using the key? 

i st. The ends of the first and second fingers should rest 
upon the button with the thumb underneath. The grasp 
should -be firm but not strained. 

2d. The movement is made by the whole hand and fore- 
arm, not the fingers. 

3d. The up stroke is not less deserving of attention than 
the down stroke; both should be decisively made, but with 
sufficient force to ensure perfect contact. 

4th. Write slowly at first, noting carefully the duration of 
spaces as well as of lines and dots. 

2. What is said of the importance of these directions? 

Neglect of some of these precautions has destroyed many 
valuable instruments and in some cases has caused paralysis 
of the fingers and fore-arm. 

2. The Alphabet.— (see frontispiece.) 1. Of what classes of symbols is the 
Morse alphabet composed? 

The Morse alphabet contains two classes of symbols name- 
ly: Visible Marks and Measured Intervals. 

2. How are th3y made? 

Symbols of the first class are made by a downward motion 
and rest of the key lever. The second class requires an up- 
ward motion and lest. 

3. How are they observed? 

The beginning of every symbol is signified to the ear by a 
click of the sounder, the first class always by a little louder 
signal than the second. The intervals of rest between down- 
ward and upward strokes are to be calculated with equal 
precision. 

1. I low many elements in each class? 

The first class contains three elements, or visible marks, 
called the dot the short dash and the lono dash. 

o 

The second class consists of four different measured inter- 



62 MANUAL OF TELEGRAPHY. 

vals, called the break, the spaced -letter- space, the letter space 
and the word space. 

5. How are tlisse intervals employed? 

ist. The break is the ordinary interval between two dots, 
as in the letters I, S, H, P. 

2d. The spaced-lctter-spacc is the wider interval used in the 
spaced letters C, O, R, Y, Z' &. 

3d. The letter-space is the interval between letters of the 
same word, as - no. 

4th. The word-space ib the interval between two words, as 
.--. Fine day. 

Give the respective values of these seven elementary sym- 
bols. 

CLASS FIRST. 

The dot is the unit for visible marks and measured spaces. 
The dot, short dash and long dash are valued respectively at 
one, three and six units. 

CLASS SECOND. 

The break is much shorter than the dot, a mere interrup- 
tion of the current in fact, and may be as short as a full and 
perfect contact on the up stroke will permit. 

VALUE. 

The spaced-lctter-spacc is equal to tv:o units. The letter- 
space is equal to three units. The word-space is equal to six 
units. 

7. What issii I of tha dot? 

The dot is not a mere point but must bear, in practice, the 
definite value of the unit, and be held firmly till, the time is up. 
The longer the circuit, the longer the time required for the 
dot, and consequently for all the elements of the alphabet. 

S. To what fault i> ihe beginner especially liable? 

ist. With the key. The beginner is in danger letting go 
the key while at work, either by accident or forgetfulness. 

2d. In spacing he is likely to space irregularly and gene- 
rally to make the interval too short between words. 

3d. In making dots and dashes he will often make the dash 
too long- and the dot too short and will separate them too far. 

4th. In long and short dashes he will shorten the long 



TELEGRAPHIC MANIPULATION. 63 

clashes and lengthen short ones, thus confounding them, be- 
yond the possibility of their being deciphered. 

5th. If letters end in dots he will invariably shorten the last 
dot. 

'.». What order is suggested for practice, by Pope? 

Pope's Modern Piuct!c2 gives the following list of ex- 
ercises: 1 st. Master thoroughly the six principles, (frontis- 
piece) of Prof. Smith. 

zd. Practice in order E IS H P 6. 

3d. " <• <• T M 5 ^ L. 

4th. " " " A U V 4. 

5th. " « •• I A, S U in couples. 

6th. " " " II V, P 4 in couples. 

7th. " •< » N D B 5. 

8th. " " - A F X Parenthesis. 

9th. u " " Comma, Semicolon \V 1. 

Observe that the parenthesis is A U run together, and the 
semicolon, A F. 

10th. Practice in order U Q^2 Period 3. 

nth. " " " K J 9 ?. 

12th. " " " G 7 !. 

13th. " « « OR&CZY. 

Note. Eoery teacher will have his preference fur particular exercises. 
These are given as specimens. The ear can be cultivated to detect these 
letters if attention is given to t /tern continually while practicing with the 
key. This will hardly create a diversion from the work of u sending^ the 
letters yroperly, and will soon come to be an important help. 

3. The Telegram.— 1 Of how many parts does a message consis.? 

The parts of a message are five in number the Date, the 
Address, the Body, the Signature and the Check. 

These are proceeded by the "office call." 

2. What is sai 1 of the date? 

The copy of a telegram furnished the operator, should name 
the place of sending, the day the month and the year. The 
month and year are seldom transmitted over the line, but 
must in all cases be supplied by the receiving operator. 

3 I. Is the date ever more minute than this? 

The hour and minute should be given if requested, other- 
wise it is optional with the operator. 

4. llow much is included in the address? 

The address contains the full name of the person to whom 



64 MANUAL OF TELEGRAPHY. 

the telegram is sent, -the city or place, the street and number 
where he may be found. 

5. What is the signature? 

The signature is merely the name of the person or firm 
offering the telegram. It should be preceded by the abrevi- 
ation siq. 

6. What is the check? 

The check is a record in the interest of the owners of the 
line giving the niunbcr of words in the body of the message, 
the amount charged and the place of payment. 

7. The body of the message? 

The body includes all matter not properly comprehended 
under any of the above heads. 

I. What punctuation is necessary? 

A period is used after the address, and after every com- 
plete sentence except the last in the body of the message.- It 
is used nowhere else, except in the body. Other punctua- 
tion marks should follow copy exactly. 

( J. What is said of abbreviations in the body of the message? 

No abbreviations are allowable in the body of the message. 
Even numbers are spelled out in full Only in such num- 
bers as one hundred and fifty, the word and is omitted, as 
well as in mixed numbers, such as« three and three-fourths, 
written three three-fourths. 

10. What of symbols? 

All symbols such as $ & @ etc. are written out thus, dollars, 

per, at, and so forth. 

II. Give a written example of both th.3 copy and of the proper form of a trans- 
mitted message. 

(The copy.) Columbus O., May, i, 1S75. 

Mason, Starr & Everett. 

Cor. 14th & Broadway, New York. 

Send us six pieces more same quality. Receive draft by 
mail. Lyman & Hall. 

(The telegram.) Fr Columbus O 1 

To Mason Starr & Everett 

Corner of Fourteenth & Broadway New York. 
Send six pieces more same quality, receive draft by mail 

Sig Lyman & Hall 
ck 10 pd 60. 



TELEGRAPHIC MANIPULATION. 65 

12. What are cipher messages? 

Words with concealed meanings agreed upon between 
distant parties are often used to convey secret information. 
Sometimes they have an allegorical sense and at other times 
no idea is conveyed except to him who has the key.. 

13. Give illustrations? 

The following are examples: 

Cincinnati, Feb. ist, 1S62. 
To Gen. Scott, Washington, D. C. 

Man Ti^er. Hyena sheep. Five paces, count thirty twelve 
seconds after. J. C Scout, 

Boston, Jan. 17, 1872. 
E. J. Fairbanks & Co. 

14 Maiden Lane, N. York. 
Bad came keen dark loud fault made short seed. 

Hardy & Goodman. 
4. Direction.-; for Checking.— 1. What words alone go free of tariff? 
The dale, the address and the signature only go free. 
When more than one signature is attached, all of them ex- 
cept the last are counted as part of thebody or the message. 
In such a case each initial is counted a word. A. M. signi- 
fying forenoon or P. M. afternoon is counted as one word; 
CO. D. (collect on delivery) is three words. 
2. Can one send his own address free? 

The following rules are adopted by the Western Union 
Company. 

The address of the sender may be transmitted free after 
the signature. The following are examples of signatures 
which may be sent free. 

Jonx Jones, 31 Bank Street. 
John Joxes. Answer. 
Jonx Jcxes. Answer at once by telegraph . 
Jonx Joxes, 31 Bank Street. Answer by teleg'h. 
Jonx Jones, 31 Bank Street. Answer immediate]}-, 
o. How are numbers reckoned? 

Numbers up to twenty are single words. Twenty-one, 
twenty-two etc. are two words. Such an expression as 12x36 
should be written out twelve by thirty-six, three, words; 24x48 
twenty-four by forty-eight, four words. 

Figures, written after numbers for accuracy, are each to be 
counted a word; thus, forty-eight (48) are four words. 



66 MANUAL OF TELEGRAPHY. 

4. How are compound words reckoned? 

Words which in Webster's dictionary are joined by a hy- 
phen are in the Western Union Company regarded as one 
word, as rail-road ship-master etc. 

Also names of persons or places, as Van Amburg, O'Con- 
nor, New York, West Troy are counted single words. But 
in names of things they are all counted, as "New England Ho- 
tel," three words, "Hendric Hudson, (name of steamer.) two 
words. 

5. How are cipher messages counted? 

Cipher messages, when composed of simple English words 
in common use, may be transmitted at ordinary tariff rates ; 
but when such messages are composed wholly or in part of 
figures, or of arbitrary combinations of letters, or of words 
of any foreign language, they should be estimated by count- 
ing each letter or figure as a word. 

6. What are half-rate messages ? 

Half rate messages are received upon some lines, and are 
transmitted during the night after all full rate messages have 
been forwarded. These are to be delivered the next day. 
1. How are the charges reckoned ? 

The charges on such messages are computed at one-half 
the usual tariff rates, provided the tariff on any message at 
half rates does not fall short of fifteen cents. Such messages 
should be written upon blanks furnished especially for them. 

8. What is the smallest number of words counted ? 

Ten words form the basis for checking in this country. 
Messages containing less than ten words cost the same as ten, 
but an additional charge is made for each word in excess of 
that number. Two or more copies of a dispatch, delivered 
to different parties, are each subject to full rates. When a 
message passes over two or more lines, the charges must be 
all prepaid or all collect. The amount charged should always 
be stated in cents. 

9. What messages are free ? 

Of course all office dispatches are free. Individuals may 
have a franchise from the company. The operator should 
make sure of this before sending messages unpaid. 



TELEGRAPHIC MANIPULATION. 67 

2— Classes and Abbreviations.— '"What classes of checks are used ? 

There are three classes of checks. The paid check, the 
collect check and the free check. The collect check is never 
to be sent unless a responsible person guarantees the pay- 
ment. 

2. What varieties are there of each class ? 

There are two varieties, the local and the through check. 
A local check is used for a single line, a through check for 
more than one. 

3. Give the abbreviations used for local checks. 

For a local message containing ten words, for which a tar- 
iff of thirty cents has been prepaid, the check reads as fol- 
lows : 

(a) io pd 30. 

For the same message to be paid at the receiving office, 
the check reads : 

(b) 10 col 30. 

On- some lines the form (a) is still further abbreviated to 
10 30 ; or 10 pel ; or 10. Form (b) appears as 10 col. 

4. Is the check ever made to cover more items than these three ? 

On some lines the "office call" of the station receiving: the 
money is inserted in the check, thus a message from N. Y. 
prepaid would be checked 10 N. Y. 30 pd. 

If the message originates in N. Y. and is to be paid in 
Cleveland, the check reads : 10 H 30 col. H being the of- 
fice call of Cleveland. If the office call is unknown W is 
used instead. 

5. How are through messages checked ? 

On through messages the check is changed by each ope- 
rator who repeats the message. The check will always spec- 
ify the tariff on the line sending it and the sum of the tariffs 
of all the succeeding lines The last check will then, of 
course, give only the tariff for that line. 

6. Give an example ? 

Suppose a prepaid message is to go over three lines, the 
first of which charges 2i cents for ten words and the sue- 
ceeding lines 30 and j_o cents respectively, the check will 
read at the first station 10 pd 25 cY. 70: at the second 10 pd 
30 & 40; at the third to pd 40. 



68 MANUAL OF TELEGRAPHY. 

7. How is the collect through meisaga checked? 

For the through message not prepaid the system of check- 
ing is directly the reverse. The first station mentioning only 
its own tariff and every other one specifying its own and the 
sum of all those that preceeded it. 

8. Give an example of collect through checks? 

Suppose the message starts from office A whose charges 
are 25 cts, and goes through B which charges 30, and C which 
charges 35 cts. The checks will read as follows: 

(At A,) 10 col 25. 

(A tB,) 10 col 30 & 25. 

(At C,) 10 col 35 & 5*5. 

!'. How are the charges paid in this case? 

The first line receives its pay from the second, the second 
gets from the third its own and the -preceeding charge, the 
last collects from the customer the whole amount. 

10. What is signified by the abbreviation "pa" in a check? 

"Pa" is an order to the receiving operator to pay the sum 
following it to the person or company mentioned, usually to 
a message boy. 

11. How are free messages checked? 

The letters D H (dead head ) are used to check a free mes- 
sage, the words, however, implying no censure, whatever. 

3. Examples for Practice. 

In the following examples 5 cts. is to be allowed for odd 
words until their sum amounts to the tariff for ten. 

1. Write on the blackboard (or paper) the check for a 
message of fifteen words over a single line on which the tar- 
iff is thirty cents for ten words. 

2. Write the local check for a message of nine words where 
the charges are 25 cents for ten words. 

3. Write the check on the following through message over 
three lines each of which charges 25 cents for ten words/' 
"Come home directly, Father is sick. 

4. Write the check on the through message over four lines 
the first two of which charge 25 cts each for ten words, the 
second and third charging 30 cts each for the same. "Good 
news from Willie and Mary, When do you sail? Don't for- 
get my friend Jennings at 17 Rue, Saint Honore, Paris."' 



TELEGRAPHIC MANIPULATION. 69 

5. Write the several checks for the through message over 
three lines which charge respectively 20 cts., 25 cts and 30 
cts for ten words. "Erie looking up, buy ^oo. Sell 1000 
Pacific Mail." 

6. Write the check for a free message of twelve words 
over each of three lines which charge severally 25 cts. for ten 
words. 

7. Check the following local message the tariff being 35 
cts for ten words: "Send 25 gross at thirty da3'S. Demand 
increasing, sold five yesterday." 

8. Check the through message for each of three lines whose 
tariff is 30 cts. for ten words. "Great Western arrived. 
Mails bring news from Frankfort on the Rhine to 25th. 

9. Write in full for transmission the following message. 
Tariff 50 cts. 

Oberlin, Jan. 25 1S69. 
J. B. Gough, Chicago, 111. 

Dear Sir, will you lecture here on the 27th inst. Answer. 
James F. Baldwin, No. 3, College St. 

10. Write in full the following message, through Welling- 
ton to New London, O. Tariff 25 & 30 cts. 

Oberlin, O. Dec. 2. 1S70. 
A. B. Chase & Co. 

Send 10 yds. best broadcloth by U. S. express, C. O. D. 

John Armor, Park House. 

11. Write in full for transmission the following telegram. 
Tariff 45 cts. 

Cleveland, O.July 3d. 1874. 
Frank B. Starr, 

227 W. 23d, Street, N. Y. 

Your stock sold. Lake Superior Pig advanced i-| per 
cent. Harvey Rice, 31, Johnson Street. 

4. The Offico Call.-l. What is meant by the "caT"? 

Each office has a "call" which may be an abbreviation of 
its name, as N. Y.,'or some one or more letters or figures 
agreed upon. The "call" of an office is also its signal or sig- 
nature. Every operator must be able to recognize his call 
by sound even though he do not read messages by ear. 



70 MANUAL OF TELEGRAPHY. 

2. On what occasions is the operator to use his own office signal? 

The operator should sign his office call to every thing he 
transmits, whether it be a call, an answer to a call, a message 
or simply conversation. 

3. What is the mode of calling? 

The operator who wishes to communicate with another 
office, makes the call of that office three or four times, and 
then signs his own office signal; repeating this operation till 
he receives a reply or tires of calling. 

5.— Cautions to be Observed by Operators.—!. What caution is given to 
insure perfect copy of a message? 

The copy should be in the customer's own hand writing. 
If the customer cannot write, the operator should not send it 
from oral communication, but write it himself and read it to 
the customer, securing his assent and, if possible, his signa- 
ture. Accuracy is all important, a slight error may involve 
great vexation and loss. 

2. What caution concerning the address? 

The address both of sender and receiver should be carefully 
kept by the operator for self-defense in case of any error of 
the carrier, and to facilitate the delivery of the message and 
its answer. It should be attached to the copy and put on 
file. 

3. How should unreasonable demands he met? 

An operator should be courteous to all sorts of people. 
Politeness and forbearance must never be laid aside however 
unreasonable the customer may be, but unjust or foolish 
requests, the operator has no right to grant. 

-1. What should be done with copies of telegrams? 

All commtmications by telegraph are strictly confidential, 
Every copy should be preserved, subject only to the inspec- 
tion of the responsible officers of the company. Messages 
received are to be filed away out of sight, the date of recep- 
tion, and hour and minute of transmission being carefully 
marked upon each. 

5. What caution is given concerning the forwarding of a message? 

The operate must never commence sendizt-g a dispatch till 
he is sure of a hearing, that is till he hears the response, "I, 
I", followed by the office signal of the receiving office. 



TELEGRAPHIC MANIPULATION. 71 

6. What if the sender detects himself transmitting a wrong word or figure'? 
If the operator stumbles, he is to say msk. (mistake) and 

go back to the last correct word. If he forms a letter incor- 
rectly he should repeat the whole word in which it occurs. 

7. What caution is given for writing to an operator who receives by paper? 
Give an operator time to adjust his register. The sender 

should make a few dots before sending the message. 

S. What extra care is given to im tired messages'? 

An insured message is repeated back to the sender, who 
carefully compares it with copy, and makes a memorandum 
on the margin of the latter certifying the correctness of the 
return and other circumstances attending the transmission. 

9. What call \i made for through messages? 

For a through message over several lines the operator calls 
the station next succeeding his own and writes "thru" on his 
message. The second calls the third and so on. 

10. When does the sending operator's responsibility for the message cease? 
The sending operator is responsible for the message until 

he receives the reply O. K. (oil korrect) "signed" by the 
receiving operator. 

11. What are the responsibilities of the receiving operator? 

The receiving operator is to compare the nu??iber of words 
in the body of the message with the check, and make sure 
that they agree, or else inform the sender and have all mis- 
takes corrected before he replies O. K. The message may 
be repeated by initials (i. e. giving the first letter of each 

word,) or in some cases the whole may be repeated for this 
purpose. 

12. What if the recc-iver i'ails to get a word? 

If the receiver is in doubt about a w r ord he should interrupt 
the message by the signal G. A. and give after it the last 
word he understood. 

13. What is the first receiver of a thru message to do? 

He is either to copy the message and send it forward or 
put the first and second stations in direct communication by 
a repeater. The second receiver does the same for stations 
two and three. 

14. How long may the receiver of a message keep his key open? 

No operator should keep the circuit open a moment longer 
than is needed to insure the perfect reception of a message. 
Other stations arc waitinc for it. 



72 MANUAL OF TELEGRAPHY. 



CHAPTER IV. 
RAILROAD TELEGRAPHY 



The following chaptei on railroad telegraphy * is designed 
to give students a general idea of the most approved methods 
of moving trains by telegraph. While the systems of seve- 
ral different railroad companies have been carefully consid- 
ered, and points from all here embodied, especial use has 
been made of the materials kindly furnished by officials of the 
Pittsburgh, Fort Wayne and Chicago Railway, and the Pitts- 
burgh, Cincinnati and St. Louis Railway. 

1. Train Itcports.—l. What arc train reports? 

Operators are required to keep a record of all trains which 
pass their stations, as well as reports of trains from other 
offices. 

2. How and Why are they kept? 

This record must be kept in a book provided for the pur- 
pose, must be written in ink, and every care must be taken 
to ensure perfect accuracy. It is often required that the train 
register, or a duplicate thereof, be forwarded to the Division 
Superintendent or Train Dispatcher, at stated times, for in- 
spection. 

3. How can operators obtain the record? 

Operators wishing a repetition of any train report, should 
apply to the Division Superintendent's office. 

4. What is the form of train reports? 

T\ie form of train reports varies on different lines. The 
eomrnon form is as follows: Alake "O S" six times and sign 
your office call; then give the number of the train together 
with the direction in which it is going, saving "on time;" or, 
it late, stating the exact time of its arrival or departure in fig- 
ures. 

5. What more is sometimes required? 

On some lines the operator is required to call the Division 

•From Mattisou's Manual, 



OF RAILROAD TELEGRAPHY. 73 

Superintendent's or Train Dispatcher's office five times, then 
sign his office call, and then proceed with the "O S" (omitt- 
ing office call after the "O S" and report as before. 

(!. How is the time designated? 

Sometimes both letters and figures are employed to desig- 
nate the time. 

7. What abbreviations are Used? 

The abbreviations are "A" or "Ar,"' for arrived, and U D," or 
u Dep." for departed. The following are examples of train 
reports: 

8. Give examples of train reports fro:n station IT, when the train dispatcher's 
ofliee is Q. 

(a) O S (six times) U. Xo 6 east on time U. 

(b) OS " U. No 6 east ar 345 U. 
(c)OS " U. No. 6 east ar 340 U. 

(d) OS " U. No 6 cast ar 340 dep 345 U. 

(c) Q^ (five times) U O S (six times.) No 6 cast ar two- 
fifteen 215 U. 

9. What is the operator's duty when a train is behind time? 

When trains are delayed behind their schedule time, the 
operator should endeavor to ascertain the cause and report 
it to the Division Superintendent's office. 

10. How are extra trains reported? 

Whenever a regular train is followed by an extra, the oper- 
ator should designate the extra as "Extra, No ," accord- 
ing to the number of the regular train which precedes it. 

J, Train Orders.— 1. How are train orders given? 

All special orders by telegraph for the movement of trains 
should be given in writing. Whether addressed to the con- 
ductor alone, or to the conductor and engineer (as is custo- 
mary on some lines,) the mode of procedure is essentially the 
same. 

2. What is the mole of procedure? 

The conductor should sign his name to the original order, 
as written by the operator, who must then repeat it back to 
the office from which the order was received, prefixing "13" 
(I understand) and annexing the conductor's signature. The 
person who sent the order will then respond "O K,*' followed 
by the exnet time, which the operator should endorse upon 



74 MANUAL OF TELEGRHPHY, 

the order. The operator should make tivo copies of the order, 
both of which must be given to the conductor, who should 
satisfy himself that they are exact copies of the order previ- 
ously signed by him, and hand one to the engineer. Both 
copies should be signed bv the operator. 

3. How much is included in a train order? 

Ail order naming any train includes all sections of such 
train, unless otherwise specified in the order. It is necessary, 
however, that the conductor and engineer of each section 
should have copies of the order. 

4. What method is used for making several copies at once? 

Iii order to obviate delay and ensure accurcy, the use of 
manifold paper was introduced by the P. F. W. &C. railway 
company, about a year ago, and the custom has become quite 
common on the more extensive railways. 

5. How can repetition of orders be saved'? 

Operators having the same order for a number of different 
trains or sections, need not repeat the order for every train or 
section, but after sending the reply once and getting the O. 
K. to it, can then add the balance of the signatures, giving 
the number of the order before each signature, and oretting 
the proper O. K. for each. 

6. What caution is given in sending figures? 

When figures occur in special orders sent by telegraph, 
they should be duplicated with a comma between. 

Operators should be positive that all copies made for deliv- 
ery correspond with the original copy received. 

7. How arc special orders numbered? 

Special orders should be numbered consecutively, com- 
mencing with No. i each week. When practicable, orders 
will be sent to the different trains named in the order at the 
i-arae time. 

8. How is the operator personally connected with a special order? 

Ill sending special orders and answering O K to the same, 
operators will invariably prefix their ov:n initial letters to 
their office calls. 

9. When several are to answer which has precedence? 

When an order is sent to more than one office at the same 
time, the station first mentioned in the order will take prece- 
dence in answerinsr O K. 



OF RAILROAD TELEGRAPHY. 75 

10. How is the receipt acknowledged? 

On receipt of an O K to an order, the operator should say, 
"I I" and sign his personal letter, signifying that he has 
received the same. 

11. When shall the reply to a special order ho made? 

Operators must not, under any circumstances, send the 
reply to any special order, until such order has been properly 
signed by the parties to whom addressed. They must use 
great caution in receiving orders for trains, and must not give 
an O K to an order unless they are positive that the train has 
not passed, and that they can put out the proper signal in 
time to stop the expected train. 

12. How are such orders kept? 

Operators will copy all special orders in a book provided 
for that purpose, and will also record on the margin of such 
orders the initial letter of the operators receiving or sending 
them, together with the correct time received or sent. 

13. How can the operator get possession of the circuit for his order? 

The signal "2" should be used by operators when they 

wish to obtain the circuit for train orders, but they must not 
use this signal when a train order or a message is occupying 
the line. This signal and the number of the order will be 
given at the commencement of every special order or reply 
thereto. 

14. How does the Train Dispatcher secure the line? 

The signal "9" will be employed by the Train Dispatcher 
or general officers of the company, and will take precedence 
over all other business. If the Train Dispatcher wishes this 
signal used to get a reply to an order, or to report a train for 
orders, he will so instruct. 

15. Who alone has a right to the sigual "!)" and O K? 

Operators in the Train Dispatcher's Office are not permitted 

to give the signal 9 or O K to train orders, until so directed by 
the Dispatcher. 

16. How does the answer begin? 

In answering an order the operator should in all cases 
begin by repeating the number of the order. 

IT. Whom are conductors of trains to address for orders? 

Communications from Conductors concerning train orders 
should be addressed to the Division Superintendent. 



76 MANUAL OF TELEGRAPHY. 

13. What is the operator's duty ^ith regard to holding a train? 

Whenever an order is sent to a station agent, operator, or 
other station employee, to hold a train for anv purpose, the 
order must be as strictly observed as if addressed to the con- 
ductor or conductor and engineer. In such cases copies of 
the order should be delivered to the conductor and engineer; 
and this must be done even when the train for which they 
were held has arrived. 

19. Is the Train Dispatcher the highest authority? 

The Train Dispatcher represents the Superintendent, and 
his rules are to be respected accordingly. 

23. What is the great rule of saf-jtr which guiles the Train Dispatcher? 

The rule of the profession is: Never move trains by spe- 
cial order until a positive response has been received from 
reliable parties, which w r ill insure the stoppage of the trains 
possessing the right to the road. If it be possible, the response 
should be from the conductor himself of the train named in 
the order. In every case absolute safety should be insured, 
even at the expense of delay. 

2. Forms of Train Orders. 

The following forms of train orders are in daily use upon 
the Pittsburgh, Fort Wayne and Chicago railway, and to the 
kindness of one of its officials we are indebted for a complete 
specimen. Although the general forms here presented are 
usually adhered to, the wording is slightly varied according 
to circumstances. 

A REGARDLESS ORDER. 

Order, No. 345. Di. 16. 

Conductor No. 4, J. 
Conductor No. 1, Kn. 

Train No. 1 will run to Massillon, regard- 
less No. 4. Answer. R. W. 

A TIME ORDER. 

Order, No. 346. Di. 16. 

Conductor No. 4, Fs. 
Conductors No. 15, Ud. 

Train No. 15 has until 3:45 P. M. to go to Lucas 
against No. 4. 

Answer. R W. 



OF RAILROAD TELEGRAPHY. 7 7 

time order — another form. 
Order, No. 347. 

Conductors No. 2 & 12, J. 

Train No. 12 can use 1 hour on time of No. 2 
to run from Wooster to Orville. 

Answer. R. W. 

A MEET AND PASS ORDER. 

Order, No. 348. Di. 16. 

Conductor No. 13, D. 
Conductor No. 16, Sv. 

Trains No. 13 & 16 will meet and pass at Woos- 
ter; No. 13 take siding. 

Answer. R. W. 

Order, No. 353. 

Conductor No. 9, D. 
Conductor No. 10, Ca. 

Trains No. 9 & 10 will meet and pass at Salem; 
No. 9 take siding. 

Answer. R. W. 

A RED FLAG ORDER. 

Order, No. 349. Di 16. 

Conductor No. 6, ) 

Conductor Extra East, J 

Train No. 6 will carry red flag Crestline to Alli- 
ance for extra passenger train. 

Answer. R. W. 

A WHITE FLAG ORDER. 

Order, No. 350. Di. 16. 

Conductor 12, ~] 

I In 
Conductors extras J 

Train No. 12 will carry white flag Crestline to 
Alliance, for extra freight trains. 

Answer. R. W. 



78 MANUAL OF TELEGRAPHY. 

A DISCONTINUING ORDER. 

Order. Xo. 351. Di. 16. 

Conductors 4th &: 5th Xo. 16. Rs. 

Fourth section, Xo. 16, will take in red flag at 
Lucas: ^th. Xo. 16, is discontinued at Lucas. 

Answer. R. W. 

ANOTHER DISCONTINUING ORDER. 

Order. Xo. 352. Di. 16 

All Conductors of Trains & Agents interested. 

Train Xo. 10. this date. Alliance to Pittsburgh. 
is discontinued. Notify all parties interested. 

Answer. R. W. 



CHAPTER V. 



PRACTICE WITH! CIRCUIT 
CHANGER. 



1. Hepeaters.—l. How is the circuit directed after passing the repeating 
relay. (/. B3Q.20 ) 

The proper direction may be given by the Ctilgan, or other 
switch; but instruments are preferred which are constructed 
expressly for the purpose and are simpler in their operation. 

2, What is Wood's button repeater? 

Wood's repeat- 
er is a compound 
switch of very 
simple form, ex- 
tensively used 
for this purpose. 
The shaded rec- 
tangle in Fig. 45 
exhibits the in- 
strument with its 
button (4) and 

r lever L. The dot- 
ted lines show 
— —the course of the 
wiresunderneath 
the switchboard. 
Wood's Button Repeater. The necessary 

batteries and instruments, except the usual local connections, 
are given in outline to assist the learner in understanding the 
arrangement. E and W are the east and west Main lines, M 
and M are the relays, S and S the sounders and B and B the 
batteries belonging to them respectively. The batteries are 
placed with opposite poles to the ground, as if they were at 
the terminals of the line 




8 MANUAL OF TELEGRAPHY. 

3. What arrangement will give two independent circuits? 

For two circuits close the button 4 and let the lever L stand 
on number 1, as in the figure. 

4. How is a through circuit pro luce I? 

For a through circuit open the button 4 which throws off 
the ground connection between the batteries; leave the lever 
L on number 1. 

5. How can the Eastern sounder 03 made to repeat into the Western circuit? 

Close button 4 and turn the lever L so as to connect 2 &:z. 

(>. How can the Western sounder ho made 1 3 repeat iuto the Eastern circuit? 

Close the button and turn the lever to connect 3 and 3. 
These two processes give two distinct circuits arranged for 
repeating. 

7. What is Pope's simple rale for the guidance of the operator? 

Rule. When either sounder fails to work coincident with 
the other, turn the button instantly.. 

8. What simpler arrangement will sometimes answer? 

If we never wish to work the two lines through in a single 
circuit the main battery is placed in the circuit between the 
middle of the lever and the ground, and the button is always 
kept closed, or is dispensed with entirely. 

9. What is the principal ohjeetion to this repeater? 

Wood's repeater requires the constant attendance of an 
operator to change the lever between a message and its an- 
swer, as is evident from questions ^ and 6 above. 

10. How is this difficulty me'.? 

In Hick's repeater the change is accomplished by a delicate 
arrangement of magnets so that the operator at the eastern 
extremity of the circuit leaves the line in the possession of the 
operator at the western extremity and vice versa. 

11. What attention does Hick's repeater demand? 

The relay needs adjustment and attention and the extra 
local batteries which assist to operate the automatic part, have 
to be kept at a uniform strength. 

12. How does Milliken's repeater differ from Hick's? 

In Milliken's repeater the automatic arrangement is pre- 
served, but the extra local battery is independent, and a 
shghtly varying strength causes no disturbance. 

13. What is Bunnell's improvement? 

Bunnell's Automatic Rep'catcr dispenses with the extra 



PRACTICE WITH CIRCUIT CHANGER. 



81 



]ocal batteries in adjusting the relay armature, and makes use 
of the principle that a current which traverses two coils of 
unequal resistance, one of which, for example is of large wire 
and the other of small, will cause more magnetic power in the 
core of the helix which has the gr -eater resistance. The helix 
of the controlling magnet is therefore of finer wire than that 
of the repeating sounder. 

14. What other advantage has the repeater? 

In Bunnell's repeater no other adjustments are required 
than those of the simple relay and sounder. Both sides also 
operate at the same time, so that the operator can alwrivs 
judge how both lines are working. 

£. Local Circuit Changer.— 1. What is the ohject of the local circuit 

changer? 

It is often important to change a set of instruments to a dif- 
ferent line. For example: Suppose a sounder is placed on 
one circuit, and a register on another in the same office. The 
operator may wish to use the register on either line. This is 
accomplished by means of the circuit changer. 

2. What is the operation of the instrument? 




A 



M It 

In Fig. 46 M and M'are the relays S the sounder and E the 

register; A and A v are the local batteries; B is a small button 

switch, having four connecting points, numbered 1, 2, 3, 4. 

When the button connects 1 and 2 the relay M works the 

under S, and M' the register. When it connects 3 and 4 



so 



M works the register and M' the soundci 



CHAPTER VI. 
RESISTANCE OF THE CIRCUIT. 



1. What is meant by the resistance of the circuit? 

All electrical currents encounter a degree of difficulty in 
passing over what are called conductors. This difficulty is 
called the resistance of the conducting medium, or of the cir- 
cuit. 

•2. Ou what doe- the amount of resislance depend? 

Many things combine to determine the degree of resist- 
ance. 

(a.) On a wire of uniform purity and size throughout, the 
resistance depends upon the length. 

(b.) If the wire changes often in size, at every place of 
diminution there is increase of resistance. 

(c.) If the conductor is made up of different substances as 
zinc, copper, carbon, brass, water, etc.. great resistance results 
at every transition. 

(d.) Many substances are poor conductors and of them- 
selves cause resistance difficult to overcome. 

(e.) Other things being equal the larger the conductor the 
less resistance it offers. The earth offers no resistance, a line 
wire great resistance. 

(f.) The battery itself offers great resistance as the current 
has to pass through many different media. The smaller the 
cells, too, the greater the resistance. 

(g.) If the plates are far apart the resistance is greater; 
also if the cells are far apart the battery resistance is unnessa- 
rily great. 

(h.) In a quantity battery the resistance is diminished by 
the number of cells; thus ten cells joined as one give only one 
tenth the resistance of one; while ten arranged for intensity 
give ten times the resistance of one. 



RESISTANCE OF THE CIRCUIT-. 83 

(i.) A dry cell or one partially dry. or otherwise defective, 
will cause great resistance. 

(j.) Pure water offers great resistance while saline waters 
offer much less. Rain in the city atmosphere causes much 
greater leakage of current than the pure rain of the country. 

3. How is resistance manifested? 

Resistance to the circuit is like friction to ordinary motion, 

it manifests itself by heat or by magnetism^ in short by taking 
some other than its original form of force. 

4. How may it often be defected? 

Any unusual heat about the connections of an instrument, 
or about a battery, points unmistakably to unusual resisicmce 
which in most cases results from looseness of the binding: 
screws. 

5. If we wish to produce heal by the current how is it effected? 

To produce heat it is only necessary to use a poor conduc- 
tor, like carbon cut thin, or to pass the current over very fine 
wire. A fine platinum wire is heated to a white heat or 
melted by the current of one cell. 

i"'. Why is the relay magnet made of fine wire? 

When the current enters the relay it is already feeble from 
the resistance of the line, but by traversing the helix of very 
fine and very long wire. The effect is multiplied by the 
number of turns of the wire without much increasing their 
distance from the core. 

7. What is the effective force of a current? 

The effective force at a station is what is left of the current 
after the loss resulting from all resistance and waste is sub- 
tracted. 

2, Measurement of Electric Force— 1. How can the resistance of different 
circuits be compared? 

The unit of resistance is called an ohm and is equal to that 
offered by 1-16 of a mile of No. 9 galvanized iron w 7 ire. A 
megohm is one million ohms. A microhm is one millionth 
of an ohm. 

5. Illustrate the use of the term? 

Suppose it is said that a certain relay offers 64 ohms resist- 
ance. The meaning is that its resistance is equal to that of 4 
miles (64-M6) No. 9 galvanized iron wire. 



B4 -JIANIIAL _0_£ TELEGRAPHY. 

Bb FTUT 3 

3. What is the rheostat? 

^Tfr^^eoslat isa coilectionof coils of wire made of an alloy 
of metal having a high resistance. ' Each coil has a certain 
i!IilTYb'er"of 'oliiils' resistance, a few having a large number and 
6trrei'5 a' smaller number in some cases down to a single ohm. 
It is analagous to a measuring pole having large and smart 
divisions marked upon it. 

4. IIow is it used"? 

■Thecurrent maybe made to traverse any number of the 

coils until its force is spent and the number of ohms of force 

to which it was equal thus known. 
p iff9fniJ '. ...... 

5. Illustrate by an example? 

\ RUP.UttU, ., , , .<l A ... 

A current may traverse one coil marked io,ooo, two coils 
3nibrucl " 

marked iooo, one coil marked ioo and three more marked 

io each. If now, tested by a galvanometer it must still show 

some force but not enough to traverse another io ohm coil. 

^rjprrop rooq j *u . . 

Lous of a single ohm are then added to the circuit till it ceases 

to affect the, needle. The sum or all the ohms on the coils 

traversed will be the measure. 

6. Do not resistance coils change their indications in time? 

Resistance coils f will endure for many vears without apore- 
ciable change, except the very slight one from temperature, 
which is known and corrected in nice calculations. 

3flJ vd 

7. What other use have they than to measure force? 

■ They are'used 'whenever it is necessary to reduce a force 

to the electrical -potential of another force, i <?'t0 make the two 

equal. Resistance coils are then introduced into the stronger 

cirtlfrt/ ; ' 

■ ' -8/ WluYt is the Ml of force? 

The unit of force or tension is called a volt, it is very nearly 

equal-to the force of one Daniell's cell. More exactly Dan- 

iell's cell=i,o7g r volt. The mega-volt==one million volts. 

jRmofj&u.p&gfirbi ; . * 

The micro : volt r one millionth of a volt. 

. 9. What is the unit of quantity? 

*' The 'unity of quantity is one farad. It is the quantity of 






electricity which, with a force of one volt, will flow' through 

a resistance of one megohm in a second. 

-^fie m ; e'ga-farad==one million farads. 

£ ^he r mrcro'- : fiirad ---one millionth of a farad. 



mem in^t 



INTERRUPTrOTT OF ~ THFT CT&CTJIT §§ 

.10. What is the unit of current? ; * 

The unit of current, derived from tnfei$t£Wffi8^rJnt 
of one farad per second. In other words if tfSic M?tM 
which would flow through one megohm of resistance^ w^rPa 1 
force of one volt, or through one ohm Wt®2£ f^^Pof" &H 
micro-volt. i'dqqm V li 

m ^ » »lo s Bi intPff .1 

I nariV/ 
CHAPTER VII. 

INTERRUPTION OF THE 

~*~~ ; I oviiosiob 

1. What are the principal forms of interrnption.of circuit? 

lhe most common interruptions are termed breaks \aiid. par- 
tial disconnections, escapes and crosses, reversed batteries and 

7 J. • 7 J • J. 7 • ' '■ '- f •(* 

electrical disturbances. , ., . 

; il 

2. What is a break? r r . ... , 

Any rupture ol the line is termed a break. 

3. What three cases arise from a break? * * 

In the first case neither of the broken ends communicates 

• i , i ■, • • i r i 

with the earth, -resulting in a total arrest of the current. 

In the second case one end communicates with the .earth. 

At that end of the line a shorter circuit is formed* at "the 
, , . . . *oqqo Y3ffj 

other there is no circuit. 

• i '■' :/< ' ! s •'- 

In the third case both ends communicate with the eajthyand 

a distinct circuit is formed at each end.- 

4. WhaUs a partial disconnection? 

A partial disconnection is formed by loose or rusty joints 
in the wire or loose screws in the instruments. 

2. Escapes and Crosses — 1. What is an escape? 

When a partial connection is formed between ■£hk ff fine and 
the earth as by moisture or dirt in the instruments, rafn on the 
posts, contact with trees or other. conductors, the loss of elec- 
trical force thus produced is termed an escape'. 

2. ^ hat is a, ground? 

A total escape is called aground. If is lrke the thrrdxase 
of a break. A complete circuit is formed' at eacWVniPbP'the 
line ;;i>J ei li 



S6 MANUAL OF TELEGRAPHY. 

3. How is an escape temporarily remedied? 

It is common to make up for an escape by adding to the 
battery. The only thing, however, which will avail is to in- 
crease the quantity but not the intensity, [p. 33.] Increasing 
the intensity aggravates the evil, while increasing the quan- 
tity supplies the waste. 

4. What is a cross? 

When two wires make a contact a cross is formed — either 
wire can be worked if the circuit of the other is opened. 
Swinging contact is a temporary or intermittent cross. 

5. What are weather crosses. 

Weather crosses are produced by a leakage of the cur- 
rent from one wire to another on the same poles, through 
defective insulation. Parallel wiies too near together some- 
times excite induced currents, which, by some writers, are 
confounded with weather crosses. 

6. How will defective ground connection affect the circuit? 

If the ground plate does not reach moist earth the effect is 
much like a cross. A soldered connection with a gas or wa- 
ter pipe is always best. 

3. Reversed Batteries.— 1. What are reversed batteries? 

When two batteries in the same circuit are placed with 
like poles toward each other they are said to be reversed. 

If the two batteries are equal no currents will pass since 
they oppose each other with equal force. 

2. How would it he at a station between the batteries? 

An operator at a station between the batteries could get a 
current from either, by putting on his ground wire, as this 
divides the line into two circuits. 

4. Electrical Disturbances.— 1. What are tba principal electrical disturb- 
ances? 

Electrical disturbances include electric storms, earth cur- 
rents, and earth-battery currents. 
2. What is an electric storm? 

The atmosphere and clouds are nearly always more or less 
charged with electricity which acts inductively upon the tel- 
egraph wires. 

When this becomes excessive as just before or during a 
thunder storm, or during the prevalence of the Aurora Bore- 
alis it is termed an electric storm. 



INTERRUPTION OF THE CIRCUIT. 87 

8. How does an electric storm affect the wii 

During these storms the wires become heavily charged and 
but for lightning arresters the instruments would be destroy- 
ed by the burning of the insulation or fusing of metals, and 
the lives of operators would be endangered. 

-1. Arc thesa storms ever experienced iu clear weather? 

A station may be at one end of a long line where the 
weather is line while the storm is present at the other, the 
disturbance will exist throughout the line. 

5. What precaution should be observed? 

On the approach of an electric storm the relays and sound- 
ers should bo removed from the circuit to guard against 
injury, 

6. What are earth-currents. 

Currents are constantly traversing the wires which are 
neither derived from the battery nor from the atmosphere, 
these are called earth currents. 

7. Do earth eurren's follow any law? 

The strength of these currents is evidently affected by the 
direction of the terminal stations from each other, i. e. they 
are usually stronger over north and south lines than over 
those running east and west. 

They are affected by the heat of the sun and often change 
with the hour of the day though not with regularity. 

8. What other cause may produce earth currents? 

They are closely related to electric storms. Although the 
tension of the earth is put at zero, yet the presence of a highly 
charged cloud over any locality will act inductively to raise 
or lower the potential or tension of the earth directly beneath 
it and determine earth currents in that direction or the oppo- 
site. The discharge of such a cloud into another more dis- 
tant would reverse the currents on that side of the locality. 

'.». When are they strongest? 

They are strongest during magnetic storms, so-called in 
which the compass needle is usually agitated. Sometimes 
they have been as powerful as the current from eighty Grove 
cells and have yielded sparks. 
10. What are earth-battery currents? 



8S 



MANUAL OF TELEGRAPHY. 



Earth battery currents are those which arise from using 
different metals for the ground plates at opposite ends of the 
line. As the earth offers no resistance a battery is formed by 
these plates precisely as if they were near together. The 
remedy is to make the metals alike. 



CHAPTER VIII. 

LOCATION OF FAULTS. 



1. Testing for a Break. Preliminary matters.— Do all statious use a 
ground wire? 

Ground wires are furnished to all stations, but only those 
supplied with main batteries use them constantly. For con- 
venience these are called terminal stations. 

2. What use would an Intermediate station have for a ground wire? 

Suppose A and B are terminal stations and F is intermedi- 
ate. E and E' are main batteries, and G and G ground 
plates. Fig . 47 

A c F " B 



y^fr- 






E' 



JQ 



n 



G G G 

If F puts on his ground wire the current from either main 
battery will go to the ground at F and return. It is evident 
that A and B can not in such a case communicate with each 
other though either can communicate with F. 

3. Must F put on his ground wire in order to communicate with A? 

If the main battery is large enough F can get a message bv 
placing his relay in the main circuit without using the ground 
wire. 



2. Testing for a Break.— 1. What special u6c has the ground wire at inter- 
mediate stations? 



LOCATION OF FAULTS. 89 

The ground wires between terminal stations are especially 
useful in locating a fault. 

2. Describe the process? 

Suppose a break to occur between F and B, as at 5, both 
of the broken ends communicating with the earth. In this 
case the intermediate ground wire will not be used. If A 
wishes to communicate with B he can get no response. The 
current enters the ground at F and returns to A. A will call 
successively on every office between B and A until he receives 
a reply. He infers correctly that the break is next beyond 
the station which first answers. B will locate it in the same 
manner. Either A or B can work with all offices between 
themselves and the fault. 

3. What is the second case? 

But if neither end of the broken wire makes contact with 
the earth, it is evident the main circuit entirely stops. No 
relay on the main line will work. Suppose F to make this 
discovery. He tries his ground w T ire for each end of the line 
and finds he can communicate with A when the current is 
directed from A through his instrument to the ground but 
not so with B. This enables him to locate the fault between 
himself and B. The process is the same at each intermediate 
station until the fault is located. 

4. What is the third case? 

If one broken end makes contact with the ground while 
the other does not, one of these methods is employed on one 
side of the break snd the other on the other side. 

3. Testing for an Escape.— 1. How is an escape located? 

The operator at A (Fig. 47) calls each station in rotation 
beginning with the most distant, and asks to have the key 
open for 2 short time. Until he passes the escape, opening 
the key will not entirely arrest the circuit as it ought to do if 
the line were perfect, but when the key is open between A 
and the fault the current is entirely cut off. 

2. Illustrate this? 

If for example the escape were at 5 in the figure, an open 
key between 5 and B would not prevent a current passing 
from A to 5 where it would descend to the ground by the 



90 MANUAL OF TELEGRHPHY. 

escape and so return to A. But when the key at F is open 
the current can not reach the escape and so can not make the 
circuit. 

3. Ho'.\- is a total escape located? 

A total escape is located in the same manner as a break. 
i. Tisting for Crosses.— 1. How i= the existence of a cross ascertained? 

If a message sent over one line returns to the same oihee 
instantaneously on another line there is probably a cross 
between the lines. 

■2, What is a possible cause? 

There might be a leakage from one wire to the other 
caused by a kite- string or other conducting substance caught 
on the wires, or by moisture, or from any of the causes men- 
tioned in the previous chapter. 

3. How i> the cross located? 

Let the key be opened at each end of one ot the lines, this 
relieves the other line from the effect of the cross. 

Xow let messages be sent by each operator in turn on the 
relieved line, commencing at B and running back to A. The 
message will come to A on both line- until it starts from a 
station between A and the fault. 



CHAPTER IX. 

TESTING BY MEASURE. 



1. Comparative Advantage of this Metho I. — 1. What objections are there 
to Hie tests described in the pi'eceeding chapter? 

These tests already given are useful only for locating faults 

approximately. In the grosser and more obvious faults they 

may be all that is necessary, but for keeping a line in thorough 

working order throughout they are wholly inadequate. 

2. Tlie Instruments.— 1. What are the instruments employed for this pur- 
pose? 

The instruments for the measurement of resistance have 
been already described, they are the rheostat and the. galva- 
nometer. 

'2, What variety of the galvanometer is best? 

Perhaps the differential galvanometer is more used than 
any other. It differs from the ordinary instrument by having 
two separate coils, a right hand and a left hand helix, of ex- 
actly the same resistance and so placed as to exert an equal 
effect on the needle. The instruments will have two positive 
and two negative terminals. 

3. How is the differential galvanometer applied? 

If a battery current is applied to two of the terminals, gen- 
erally the two central ones, as the resistances are equal, one- 
half of the current will pass through the right-handed helix 
and the other half through the left handed one. The needle 
will therefore remain quiet. Now if equal resistances be 
added to each coil the needle still remains motionless, but if 
unequal resistances be added the H" pole of the needle will be 
deflected toward the side which has the least resistance, as 
this allows more electricity to pass than the other. 

4. Will a galvanometer hear the whole power of amain battery? 

The current of a large batter}' would be likely to destroy a 
galvanometer helix even if divided as in the differential appa- 
ratus. 



92 MANUAL OF TELEGRAPHY. 

5. How is this avoided? (See Appendix A. 

The instrument is provided with a shunt or loop which has 

a resistance exactly equal to 1-99 of that of one of the coils of 

the galvanometer. Accordingly when the battery current is 

turned on, 99-100 of it passes through the shunt and only 
1-100 through the galvanometer. 

9. How is the differential galvanometer changed to one of the ordinary kind? 

The current can be directed through either of the coils 
singly, the other being "cut out." when it will be in suitable 
condition for ordinary testing to find broken connections, loss 
of insulation &c. 

3. Practice wtth th? Gih':in?m r ter.—llvx of:en s'.ival.l the lin? he exam- 
ined with the galvanometer"? 

The resistance of every main line circuit should be meas- 
ured every morning, and much oftener if there are marked 
changes of weather, and the mean of all the resistances should 
be recorded. 

2. How is the line prepared for testing? 

Every key is closed and the ground wires are taken off, 

leaving the line perfect!}' insulated throughout. This gives 
it the same tension in every part. 

3. How is any current at all to pass such a line'? 

If there were no escapes in any part of course no current 
would pass, and this is precisely what is to be ascertained.. 

4. How much resistance ought such a line to show? 

If again the insulation were perfect such aline would offer 
infinite resistance; although the current would Jlozv into it, 
and give it a potential equal to that at the battery. The 
needle would stand at o. 

5. In practice how much feslstan -e i- : csd; allowing f j'r uuavc 
escapes? 

Even in wet weather a line in good order, of two hundred 
miles length, ought to show a resistance of 5000 ohms. If we 
try half the same line, of course we have now only half the 
escapes, and the resistance is, therefore doubled. For a single 
mile the resistance should be 200 times 5000 ohms, or a meg- 
ohm. 

6. Suppose there is considerably less resistance than tfyis? 

If the resistance is much less it proves that there is unnec- 
essary, or at least unusual escape, somewhere, and we pro- 
ceed at once to locate it. 



TESTING BY MEASURE 93 

7. What is the counter-test? 

The counter-test is made by putting- on the ground at one 
terminal while the galvanometer is applied at the other. The 
ground wire if perfect gives a total escape, and the other 
escapes are nothing in comparison. 

8. Why will the current then flow? 

The .current .always flows toward a point of lower poten- 
tial. The potential at the battery may be be taken at ioo, the 
potential at the other terminal is o. And at any point on the 
line it is in exact proportion to its distance from the battery. 

9. IIow then can we now ascertain whether the line has the proper.xesist- 

anct? 

The resistance in this case increases with the length. If 
each mile of No. 9 galvanized wire give a resistance of 16 
ohms when perfectly insulated except at the terminal, then 
200 miles should give 3200 ohms. 

10. Suppose the resistance too low, how now is the fault locate,]? 

First we suppose that by frequent measurements the. pro- 
per resistance per mile is known. Now if the broken line 
makes full. contact with the earth the resistance of the broken 
line divided by the resistance per mile gives the distance of 
the fault from the operator. If the test at the other extremity 
gives a corresponding result the location is perfect. 



11. How «lo we know whether the break does make full contactor not? 






If the contact at the fault is imperfect as is generally the 
case the resistance of the broken line is now gi'catcr than that 
of the whole line with a ground w T ire at the terminals and the 
same experience is found at each terminal station. 

1-2. Illustrate by a case of perfect contact? 

Suppose the line to be 100 miles long and that its average 
resistance is 1400 ohms or 14 ohms to the mile. If now the 
test at A one extremity of the line shows 854 ohms resistance 
this indicates 61 miles. If the test at B gives 546. ohms it 
indicates 39 miles and the fault is located. 
13. Illustrate a case of imperfect contact? 

Suppose the test at A, one end of a one hundred mile line, 
to indicate 76 miles and the test atB to indicate 32 miles. This 
is 12 miles in excess of a hundred. The first indicates the 
fault 76 miles, say west, from A, the other points to 32 miles 
east of B. The true place is midway between .the two local 
ities indicated. 



94 



MANUAL OF TELEGRAPHY. 



14. Will this metlioi! apply to any other fault than a break? 
This applies to any fault arising from increased resistance. 
A careless operator has had a defective connection traced into 
his very office by a skillful tester fifty miles away. 

4. The Loop Test.— I. What is the loop? 

The loop is made by connecting the faulty wire with a per- 
fect one running from the same office. The connection is 
made at a station beyond the fault and as near to it as may 
be ascertained without measuring. 

•2. Why is tb.3 loop tost preferre I? 

This test is more accurate, and can be used whatever be 
the resistance of the fault itself. It is therefore available for 
a varying resistance. 

3. Describe the test for an escape in general terms? 

The method is first to measure the resistance of the loop, 
and if we know from the record what the resistance of the 
two wires constituting the loop should be, when there is no 
fault, then half the difference between the recorded and the 
present resistance is the distance in ohms of the fault from 
the distant station. 

4. Give the steps for finding the resistance of the loop? 

B Fig. 47 represents a carbon batteiw. The current ascends in 
the direction of the arrow to a the common terminal of the 
two coils of the differential galvanometer G. Here the current 
divides and after traversing the two wires of the galvanome- 
ter one branch of it flows to the right through the loop, which 

Fig. 48. 










TESTING BY MEASURE. 



95 



begins at M" and passing around by the distant station S 
returns to the battery. The other branch Bows to the left 
through the rheostat E, and hack to the battery. The por- 
tion from M through R and N to the battery is all in the 
office. 

Resistance is added in the rheostat until the needle stands 
at zero. This gives the resistance of the loop. If the cur- 
rent is too heavy for the galvanometer a portion of it may be 
passed through the shunts x y z. The currents returning to 
the battery reunite at K. 

5. If there is m record of the proper resistance how i» the fault located? 

There are two cases. First suppose the two lines, when 
both are perfect, to be of equal resistance. First ascertain the 
resistance of the loop as in question four. Next put the neg- 
ative wire to the ground as in tig. 49. 

The current as before will pass from B through the key 
and divide at a and on leaving the galvanometer the two 
branches will go to right and left and meet at the fault [ F both 
returning to the battery through the ground from F to G' and 



Fig. 49. 




B, the wires which cross at K not touching each other. Re- 
sistance enough is put into the faulty wire by means of the 
rheostat it to make the needle balance. Tin's resistance must 



9 6 MANUAL OF TELEGRAPHY. 

of course equal that of the small part of the loop from F 
through S to D. The points D and F being equi -distant from 
the station S. Therefore, half the resistance which we have 
added in order to make the needle balance, is the distance in 
ohms of the fault from S. 

Suppose the resistance of the perfect line is recorded at 
ioo ohms, and that of the faulty one when perfect at 9S ohms. 
If now the fault should be 22 ohms from S, it is evident that 
the resistance on the perfect side of the loop from the galva- 
nometer around to the fault is 122 ohms; while on the rheo- 
stat side of the loop it must be 46 + 76 ohms, because 9S — 22 
= 76, and we must add 46 more to make up .122, before the 
needle is balanced. From the 46 added, take 2 ohms, which 
is the excess of the perfect line over the other, and we have 
44. One half this is 22 ohms = the true distance in ohms of 
the fault from S. 

G. How may we find the distance of the fault from the operator directly? 

We may add all the resistances together 1224-76-1-46=254, 
and one half this is the distance in ohms of the fault from the 
galvanometer over the perfect line. This same quotient (122) 
minus 46, the resistance added, and minus 2, the difference of 
the two lines, gives 74 the distance in ohms of the fault from 
the galvanometer over the bad wire. This divided by the 
resistance per mile gives the number of miles. 

7. What is the object of referring to the recorded resistance-? 

The recorded resistance taken zi'iili the groiind zi'fre on 
when divided by the number of miles srives the resistance 
per mile. 

8. Is the resistance per mile the same when there is an escape? 

Even perfect contact of both ends of a break with the 
earth will not alter the resistance of the loop since the cur- 
rent has to traverse only a few feet of earth which offers no 
resistance and then resume its place on the wire. Much less 
will an escape effect it. 

0. What better is the record than a new test? 

The record will tell whether the two halves of the loop 
have the same resistance or not. While a test taken when 
the loop is made will necessarily make them alike. The error 
from this source is small. 



TESTING BY MEASURE. 97 

10. In what case is the record indespensable? 

In case one end of a break is left in the air while the other 
makes earth no current will come through a loop. But the 
record giving the sum of the two resistances is as good as if 
we had a loop. Then testing each end of the loop the one 
in the air will give a very high resistance and the other will 
give a resistance which at once reveals its distance in ohms 
from the break. 

11. Suppose both ends of a break are left in the air? 

If both ends are insulated, then both the perfect and the 
faulty wire, when the loop is joined at S will show high 
resistance and thus reveal the fact. We must now compare 
the recorded resistances of the two wires when insulated 
with the resistance which each side of the loop now offers. 

In this case it is only necessary to divide the resistance of 
one mile by the greater of the two resistances given by the 
different sides of the loop. 

12. Give an example? 

Suppose a loop 200 miles long has a resistance 5,000 ohms, 
that is one megohm per mile. On trial, one side of the loop 
gives 8333^ ohms resistance. The other side gives 12500. 
Dividing 1,000,000 by 12,500 we have So the distance of the 
fault in miles. 

If we divide t, 000,000 by $333-^- we get 120 the distance of 
the fault measured over the perfect side of the loop. 

RULES. — These results for convenience are embodied in 
a briefer form. The two following rules apply when the 
broken ends of a wire make earth, or when there is an escnpe 
only; and when both halves of a loop have the same recorded 
resistance: 

Rule 1. One half the difference of resistance between the 
perfect side and the faulty side of the loop, divided by the 
resistance per mile, equals the distance of the fault from the 
station where the loop is joined. 

Rule 2. One half the sum of all the resistances in circuit 
divided by the resistance per mile of the loop and subtracted 
from the whole loop is the distance of the fault from the oper- 
ator. 

When the recorded resistances of the parts of the loop differ. 

7 



9 3 MANUAL OF TELEGRAPHY. 

Rule 3. Subtract the resistance in the rheostat from the 
resistance of the loop. Half the remainder divided by the 
resistance per mile of the loop is the distance of the fault. 

When one of the broken ends is insulated and the other 
not. 

Rule 4. Find, by the galvanometer, which side gives a low- 
resistance- Divide that resistance by the resistance per mile. 
The result is the length of that part of the loop between the 
operator and the fault. Or: 

Rule 5 Divide the recorded resistance per mile of insulated 
wire by the resistance of the insulated part ot the broken 
wire. The result gives the length of that wire in miles be- 
tween the instrument and the fault. 

13. Examples for practice. 

i. A loop 80 miles long has a resistance of 960 ohms, the 
two halves being alike. The rheostat needs 2SS ohms to 
make the resistance of the faulty side equal to that of the per- 
fect side. Required the location of the fault. 

Ans, 2S miles from A. 

2. Loop 160 miles, recorded resistance 1920 ohms, differ- 
ence of faulty and perfect side 336011ms. Required the loca 
tion of the fault. Ans., 66 miles from A or 14 from S. 

3. Loop 40 miles, recorded resistance of perfect side 260 
ohms, do of faultv side 250 ohms. The needle balances be 
tween the faulty and perfect sides of the loop when 51 ohms 
are inserted. Required the location of the fault. 

Answer, iS Miles from A. 

operatic:-:. 

Resistance of Loop 510 

" ' Rheostat - - - - . - 51 

Difference 459 

5 10-*- 10=12.75 the resistance per mile. 

If + 12-75 = iS, Ans. 

(Examples for practice.) 

Ex. 4. A loop of 120 miles lying west of A. has a recorded 
resistance of 1440 ohms, and 96 ohms are required in the 
rheostat to balance the needle. How far is the fault from A. 

Ans. 56 miles. 



TESTING BY MEASURE 9 9 

Ex. 5. A loop of 1S0 miles lying west of A, has a record of 
5555i ohm's (insulated) resistance. A break with one end 
grounded and the other insulated has a resistance on the 
insulated portion of 1 1626.7 ohms. On which side of the 
break is the wire grounded? How far from A is the fault? 
Arts., On the east side. S6 miles from A. 

Ex. 6. A loop whose record is 12 ohms per mile uninsu- 
lated and one megohm per mile insulated, requires 360 ohms 
to balance singly the faulty side of the loop and 29720.97 
ohms to balance singly the perfect side. 1. What is the na- 
ture of the fault? 2. How far is it from the station A? 
3. How long is the loop? 

Ans. 1. A break with wire aground on the faulty side. 
Ans. 2. 30 miles. Ans. 3. 67 miles. 

7. A loop west from A has a record of 1,200,000 ohms per 
mile and a total resistance of 20,000 ohms. The southern 
branch requires 10,859.7 ohms to balance the northern which 
gives 46,153.8 ohms. 

1. On which branch is the fault? Ans. U". 

2. What is the nature of it? Ans. 

3. How far is it from A? Ans. 26 miles. 

4. How long is the loop? Ans. 60 miles. 

Ex. S. The recorded resistance of an 80 mile loop is 18 
ohms per mile. The loop test, however, gives a resistance of 
1300, while the differential test requires an addition ot 130 
ohms to the faulty side. 

1. What is the fault? Ans. Break with partial earth. 

2. W T here is it? Ans. 36 miles off. 

Ex. 9. A wire out of Albany has five stations distant 
respectively 7, 1 7-> 2 4-> 33 an( ^ 4 3 miles from A. 

This wire has a resistance of 13 ohms per mile. A parallel 
wire through the same stations has a resistance of 12,75 OQms 
per mile. A test shows a resistance on a certain day of 1344 
ohms for the loop, and a differential resistance of 2SS ohms. 
Required, the nature and location of the fault. 
Ans. Bad connection at the fouith station. 

Solution. We know it is a bad connection of some sort 
because the resistance is more than ordinary. Now the sum 



100 MANUAL OF TELEGRAPHY. 

of the resistances 1344+288 divided by 2 and by 16, the aver- 
age resistance, gives 51, which taken from the whole loop 
leaves 33 the distance of the fourth station from Albany. 

6. Location of Crosses by Mjasare.—l, What is the simplest case of this 
fault? 

The cross easiest to locate is one in which the two wires 
make a good contact so as to form a loop. We have then 
merely to make the loop perfect by opening the key beyond 
the fault on both wires, and then to measure the resistance 
of the loop. This divided by two and by the resistance per 
mile will locate the fault. 

2. Snppo-o the contact is not perfect? 

If we have reason to suspect there is resistance where the 
cross js made, then each wire should be tested by the loop 
method with a third wire which is perfect. While one of 
the cross-wires is being tested the other should be grounded 
at both ends. The tested wire will then make ground through 
the cross, and the location may be found exactly as if the 
cross w r ere a break, with imperfect ground at the broken end. 

3. What is Culley's method? 

In an extremely neat method given by Culley the differen- 
tial galvanometer is employed as follows (Fig ^o:) 

Let X and Y be two wires which cross at F. S is a station ' 
beyond the fault. Connect the carbon of the battery B to 
the wire X, and the zinc to the galvanometer, at the common 
terminal of both coils. Yis connected with the galvanometer, 
and the distant end is grounded. The remaining terminal of 
the galvanometer is also grounded. 

The current will divide at F one branch of it going on to S 
where it reaches the ground and returns through the earth to 
the galvanometer and battery. 

The other branch of the current returns over Y from F and 
traversing the other coil of the galvanometer reaches the bat- 
tery. 

Now as the earth makes no resistance if F is in the middle 
ofX the needle is balanced. If not, the resistance necessary 
to make it balance will show the difference ot resistance of 
the two sections. 



TESTING BY MEASURE. 
Fig. SO. 



101 



S x 



^\ r 



V 



B 






\ 



i. 



4- What is Blavicr's formula? 

Blavier's formula is as follows: 

Let X equal the resistance of the shorter portion of Y. 

" L " " of the whole line Y. 
'" R " " added to the shorter portion. 

r „. _ L-R 

Then X= — 2 — 

Ex. 1. The resistance of a certain line Y was recorded at 
700, or 14 ohms per mile. On testing for a cross a resistance 
of 100 ohms was necessary to balance the needle. Required, 
the distance of the fault. Ans. 28,58 miles. 

Ex. 2. A wire 40 miles long had a resistance of 13 ohms. 
On testing for a cross (as in Fig. 50) the needle of the differ- 
ential galvanometer remained at zero. Required, the distance 
of the fault. 

Give the reason of this answer. 



CHAPTER X. 
LAW OF RELATIONS. 



Note. Hitherto we Have explained the methods in use for detecting 
haults without employing what is knoion as Ohm's law, preferring to have 
the student thoroughly familiar with processes of easier comprehension 
first, lite law. however, admits of easy explanation at this stage of the 
work and man be readily comprehended by one acquainted with the sim- 
plest mathematical operations. 

. — *-•— 

1. JSleciro-motive Force.— 1. On what does electro-motive force depend? 
With a given battery the force depends on the number of 

ceils in line. 

2. What experiment proves this? 

Connect a Daniel's cell with one coil of the differential gal- 
vanometer and insert the whole resistance of the rheostat in 
the circuit. A very small deflection of the needle will be ob- 
served. Now add one cell to the battery so as to double the 
intensity; the deflection of the needle is doubled. A third 
cell will treble it and so on. 

3. How does the size of a cell affect it? 

The size is unimportant. A small cell yields the same 
force as a large one. If a small cell and a large one are op- 
posed to each other no current will pass and the needle is not 
deflected. 

4. How do two or more cells joined as a quantity battery affect the needle? 

The quantity battery is the same in effect as a battery of 
large cells; the force depends wholly onthe number used for 
intensity. 

5. lias quantity nothing to do with the deflection? 

The needle is controlled by the quantity which traverses 
the galvanometer wire and not by the quantity present in the 
battery. The latter is in a measure static until sent forward 
by the force which we call tension and which acts as a spring 
or pressure to move the quantity. 

6. Illustrate this by an analagous case of force? 

An analagous instance is afforded by two open basins of 



LAW OF RELATIONS. 



103 



water of different size and connected by a tube at the bottom. 
Let the basins be filled one inch at the same instant and kept 
supplied to that level. 

Fig. si. 

B 



J! 



„_ 



It is evident that as soon as the tube T is filled the pressure 
is equal throughout and that there will be no current in the 
tube. Now enlarging either basin of water, or adding others 
on the same level (quantity battery) will create no current. 
But if we increase the height of the water in either basin (in- 
tensity) a current at once sets toward the other. 

7. How is resistance explained by the same apparatus? 

High, insulated resistance is represented by taking off one 
basin and closing the tube at that end, the pressure (tension) 
remains, but no current flows in the tube except at the mo- 
ment of filling it, exactly as it is with a resistance coil or long 
wire. This tension is proportioned to the number of inches 
of height o£ water in the basin — corresponding to the num- 
ber of cells of battery used in electricity. 

7. How arc other forms of resistance illustrated? 

By making use of a long tube and opening the end most 
distant from the basin, we illustrate the effect of a ground 
wire (Fig. 52.) The friction offered to the current by the 
tube, makes a resistance exactly proportioned to the length of 
the tube and the pressure (tension) inside the tube continu- 
ally diminishes till at the open end it is zero. Making the 
tube smaller w 7 ill diminish the quantity of the current, just as 
a small wire will transmit less electric force than a large one. 
Making it longer will diminish the current in the same way. 

Every leak will lessen the resistance and drain the force 
while every stoppage will have the opposite effect, as is the 
case on a line wire. 

8, Howis the running of several wire ; f ora one bfittery illu tratccl? 

We are to imagine the water capable of keeping its own 
level in the basin up to a certain limit. Now if branch pipes 



104 MANUAL OF TELEGRAPHY. 

extend from the base, so long as this level is maintained they 
are all supplied, and if of equal size and length cany the same 
quantity of water. Change any of these conditions and that 
branch discharges most which is of largest calibre and short- 
est length, i. e. of least resistance. 

9. In branch circuits what is found to be the law of the quantity cf electricity 
passing in each? 

The quantity of current passing each branch of any two 
wires is an inverse ratio to its resistance. Thus if the resist- 
ance of one is ten times that of the other, then one tenth as 
much will flow in that one as in the other, or one eleventh of 
the whole. 

10. What is <he rule for finding the joint resistance of branch circuits or 
shunts? 

To find the joint resistance of circuits, multiply tneir resist- 
ances together and divide the -product by their sum. Or: 

EXE 

For three or more circuits, find the joint resistance of two 
and then the joint resistance of this result with a third and so 

on. 

11. What is Ohm's law of electric relations i 

Ohm's law is that the quantity of electricity which passes 

any point in a ivire, varies directly as the force, and inversely 

as the resistance. 

F 
It is expressed by the formula Q oo-p- 

If the units of force and of resistance have a fixed ratio then 

^ F • p , i . Xo. of volts. 

O = — i- e. The number of farads per seconcl=— — ; 

^ E * .No. megohms 

12. How may the formula be varied? 

When resistance is constant (i. e. a fixed number of meg- 
ohms) then Q^ qo F. If F is constant, Q^ oo — and finally 
to produce a constant quantity, F must vary as R. 

2. Resistance of Batteries and Short Wires— 1. How is the internal resist- 
ance of a battery measured? (See Appendix B.) 

To measure the resistance of the battery itself, first send a 
current through the galvanometer, using the shunt (A, ap- 
pendix,) so that only i-ioo actually passes; and using no 
resistance coil, note carefully the deflection of the needle. 



LAW OF RELATION. 105 

Xext insert resistance coils between the galvanometer and 
negative pole of the battery until the needle falls back to its 
first position. The number of ohms used multiplied by ioo 
will be the resistance sought. 

2. How is the resistance of short wires and office connections found? 

To measure the resistance of short wires first find the R of 
the battery as above, then place whatever is to be measured, 
in circuit, between the positive pole of the battery and the gal- 
vanometer, always using the shunt. Insert resistance coils 
between the galvanometer and the negative pole. Subtract 
the resistance of the battery from the whole resistance thus 
found. 

3. When does the resistance of the battery become important? 

In all measurements for resistance, that of the battery and 
office wires traversed should be taken into account, other- 
wise miles of error may mar the reckoning. But in a short 

circuit the resistance of the battery is of transcendant impor- 
tance. 

4. Why is this? 

Suppose a battery has 30 ohms resistance. This is equal 
to that of two miles of the best line known. But suppose the 
wire is but a few feet in length the resistance of the battery 
may be a thousand times that of the wire. 

5. Illustrate by experiment. 

Clark gives the following curious experiment which fur- 
nishes at first an apparent contradiction of Ohm's law. Place 
the shunted galvanometer in the circuit without resistance 
coils, and notice the deflection of the needle with one cell. 
Now add a second cell to the circuit and note the deflection. 
We have doubled the force but the increase of deflection is 
hardly noticeable. Add a third and a fourth or even five- 
hundred cells and the needle is not changed. 

G. How is this accounted for? 

Each cell brings as much resistance as it does force. In other 
words the resistance, from the shortness of the circuit, being 
nearly all taken away, the electricity of the first cell escapes 
before that of the next overtakes it so that no pressure is 
added. 



106 MANUAL OF TELEGRAPHY. 

7; How only can the force become evident? 

There must be sufficient resistance to check or dam up the 
current so that it shall set back as it were and allow the ten- 
sion of each cell in succession to act on the next following, or 
to speak less figuratively, a certain portion of the quantity 
gene'Jfcted must become static in order that it may have a 
base on which to react before its power is revealed. 

8. How is this conformed to Ohm's law?* 

Suppose the resistance of each cell 30 units and that of the 
galvanometer wire 4 units, then the quantity for one cell is: 

( ^ = lu^H for thiee cdls ^ = 90+T = ~3T ncarl Ji for 5°° 

cells ^ = ^5ooTT=^(r nearl - v - 

It seems then that the quantity traversing the wire is 
scarcely changed, and hence the deflection should change 
but slightly. 

9. Does this static electricity exhaust the battery? 

There is no waste of battery by the static portion of the 
iorce. When the current ceases to flow on account of infin- 
ite resistance, ail the force is static, and the battery remains 
intact. If a battery capable of yielding 100 farads per second 
can get away but 60, on account of resistance, then the con- 
sumption of 40 per cent of zinc is saved. 

3. Practical Application, of Ohm's Z:nv.-1. What is the effect of escapes 
or grounds upon the batter}-? 

Applying Ohm's law Q_ equals F over R, since escapes 
diminish the resistance of the line the value of the fraction, 
F divided by R, is increased. A greater quantity, therefore, 
escapes which rapidly exhausts the battery. 

2. Is the power to work signals greater or less in wet weathei ? 

Since in wet weather the resistance is less than in dry, 
more electricity leaves the battery, but being diverted from 

* Note/ 100) hcre'has no meaning except as a mere basis of comparison. That 
K it is not aw// or any other recognized unit of force. A Grove battery which 
has but 5 ohms resistance would have at most but about 10 volts of force. ( \p- 
pendix 13.) This, to avoid fractious of high denomination may be put a' lOCO.and 
then since 1 mega-farad of quantity equals 1 volt divided by 1 ohm, the answers 
in the following cases if divided by 100 will be in mega-farads, or if multiplied 
by 10,000 will be in farads. In all cases, Q in mega-farads equals « volts divided 
by?« ohms; or Q in farads equals 10,0^0 « volts divided by m ohms, (See page S5 Q. 
10.) Jf.we wish, however, merely to compare the quantity issuing from two dif- 
ferent batteries, then an imaginary unit is a'l that is necessary. 



LAW OF RELATION. 107 

the offices, the working power at any station is less than usual. 
The working power depends upon the quantity passing 
through the instruments. 

3. Give Pope's example of finding- the working power at a station. 
This requires us to find the quantity by Ohm's law. Sup- 
pose a well insulated line, A B with the ground wires on, has 
a resistance of ioo ohms 

The batteries 5 each, 10 rt 

The instiuments 10 each 20 " 



Total resistance 130 

* Let the force of each battery equal 1000 units. 

rpi r. 2000 _. . 

Ihen (4^ = - — ■ = 15 4 Ihe working power 

-LoU 
A Fig. 63. 

E r ~ 



5 5 



m. , m 

4. Suppose an imperfect ground between E and E' wliich offers a resistance of 
50 ohms? 

Since the batteries are exactly opposite one another as 
respects the fault, no effect is produced while the circuit is 
closed at both E and E'. When either key is open, however, 
the effect is the same as if a wire having 50 ohms resistance? 
extended from the middle of the line to the ground. 

Fig, 54. 

A F B 



+ r®<$eW [&&& 



50 : 5 

! 



EL , L m 

Suppose A opens his key, the circuit from his battery E is 
broken. From B there is a circuit around by the fault. Using 

F 

Ohm's formula Q, = — ; — we find the working power of 

this circuit as follows: 



MANUAL OF TELEGRAPHY. 
Battery resistance, ohms 

Instrument " t " 

Half line 

Fault, " f • 

50 " 

Total " ~ 

trvtwhe'rf IO0 °'- Cl eqiU ' IS IO °° * '5 e ^ h S 7- But on 
Q' eat, 1 ex ^"™ ent « ^e opposite station, B's current. 

C* equals i >4 . Subtracting Q_ from q> we hav£ 6 ft 
working power. '' 

5. What it the tiu.lt were near A? 

The current from battery E would then divide at the fault 
a part returning by the fault and a part going around by B s 
goundwn-e. The resistance will then b°e as follows: it A' 

« okms totT , IO °° hmS ' !nStrUment a " d batte " es equal 

ohms " 5 ■ Resistance ° f ">e fault equals 50 

Their joint resistance is iggj equal 34.8 ohms. 

To this add resistance of battery E and instruments. The 
total resistance is 49.8. 

Q, therefore, at battery E equals i™_ equals 20 
C What portion of the current will go over each branch' 
The resistance by one route is 1 ,5 ohms. By the other it is 
50 ohms. „ s + 50 eqnah l6 , So U5 Qf 2q win ^ ^ w ^ 

of die fault, and «L of 20j 6 , wi „ go ^ the ^ fo fi 

The division of the current horn B' can be found bv a mode 
piecisely similar. Thus 

Joint resistance of the two branches = I5+50 — 

D • 15X50 ~ "5 

Kesistcnceof line, battery E and lusts. Ii; . 

Total resistance 126.5 ohms 

The Q] from V is, therefore, 2™ equals 7 . 9 . 
The resistance of the two circuits beyond the fault being 



LAW OF RELATION. 109 

15 and 50, 15 parts will go to the ground at F and 50 will go 
around by the instruments. 

7. How much current will there l)3inB's iu striiirisnt when A is sending"? 
In sending, A will alternately open and close his key. 

When he closes it the strength of both batteries will reach 
B's instrument, that is 7.9 + 6.1 equal 14. But when he opens 
his key he cuts oft' the current from his own batten - , while 
from E' is a force of 6, r. 

The difference between 14 and 6,1 is 7,9 which is the avail- 
able force at A to work B\s instrument. 

8. How much in A's instruments \vh3n IS is sending? 

When B closes his key he has the current, which leaves 
battery E, equal to 20, added to his own current, 6.1 making 
26,1. But when he opens his key his own current is cut oft', 
and from battery E. we have 1003 divided by 65 as in the 
first part of the example, equals 15.4, which taken from 26. 1 
leaves a working current of 10.7. 

9. Plow large a Grove battery would this imply? 

According to the foot note on p. 106 this implies a battel y 

power equal to about 6,1 Grove cells. It is ascertained as 

follows: Dividing the working current by ioo we have ,107 

F 
megafarads. Now as Q^ equals — — - by substituting figures 

for Q^ and R, the equation becomes, .107 =: * — that is, F 

x.LO , 

equals ,107 X 115, or F equals 12,20 volts. One Grove cell is 
by the table, (nearly) two volts. Q_, therefore, equals the 
quantity sent over a resistance of 115 ohms by a battery 
power of 1 2. 2o -*- 2 equals 6.1 Grove cells. The power of 
about 4 cells would therefore be wasted by the supposed 
fault 

10. What would Lc the effect of doubling A.'s battery. 

doubling A's battery will double both' its force and its resist- 
ance. F must be reckoned 2000 instead of 1000 and R 10 
instead of 5. Proceeding as before the effective current 
which A can use in B\s instrument is 12,6, which, as the 
resistance is now 120, will be the current furnished by seven 
and a half Grove cells, 15 being employed. B would have a 
current of 13.4 or a little over eight Grove cells. 



110 MANUAL OF TELEGRAPHY. 

12. Would it b3 better to double B's battery? 

Doubling B's battery while the fault is near A, will increase 
the working power fromB through A's i-nstrumeats, but give 
A less power through B's instrument. 

12. What three practical results have we then? 

i st. When batteries and instruments are equal at each end 
of the line, a fault midway between them does most mischief. 

2d. The station farthest from the fault gets the weaker 
signals. 

3d. The increase of battery should be made as near the 
fault as possible. 

13. How are the main batteries usually placed? 

Half the main battery is usually placed at each end of the 
line, unless one end is necessarily more defective than the 
other. 

14. Why not place all the battery at one end? 

There are always more or less escapes and a battery wholly 
atone end, therefore, works unevenly. 

15. Why not put it in the middle? 

It is essential that the terminal stations have control of the 
current. If the line were faultless and sure to remain so the 
location of the battery would still be at these stations. 

4. Blavier's Method Without a Loop.— I. What occasion may render the 
loop test impossible? 

There is sometimes but a single line, or if there are many, 
the prostration of a few posts may render them all faulty at 
once. 

2. What merit has Blavier's method? 

Blavier's method is quickly and easily accomplished, and 
requires but one skilled operator. An assistant of ordinary 
intelligence being sufficient at the distant end. 

3. What data are necessary. 
Three things must be known: 

1st. The ordinary (uninsulated) resistance, (R,) of the wire 
from the records. 

2d. The resistance (S,) of the faulty line (uninsulated.) 

2. The resistance (T,) of the faulty line, insulated at the 
distant end. 

4. Suppose R, S and Tare known what is Blavier's rule. 



LAW OF RELATION. 1 1 1 

RULE. Square S, multiply T by R, and add the products. 
From this sum take T times S, and also R times S. Extract 
the square root of this remainder and take it from S. This 
gives the resistance of the portion between the station and 
the fault. It is reduced to miles by simply dividing it by the 
average resistance per mile. 

5. Give the same rule in a formula. 

Putting D for the distance of the fault, and A for the aver- 
age resistance of the line per mile when not faulty, the equa- 
tion is as follows; 

G. Illustrate the rule by au example. 

Ex. Let R, from the record, be ioo ohms, with an average 
of 12 ohms per mile. 

Let S by measurement equal 92 ohms. 
" T " " 64 » 

Substitute these numbers for the letters they represent in 
the formula and we have. 

D= ^2-, S446 + 1 C4UO-1508SQ)200 nn| , n , s f m ; ]cc 
12 

Ex. 2. A line from Haverhill to Lyme, 17 miles has a 
record of 204 ohms, or 12 to the mile. A measurement for a 
fault gave a resistance of only 1S0 ohms, when the line was 
uninsulated, but when the ground wire was taken off at Lyme 
The resistance at Haverhill was 320 ohms, where was the 
fault? 

Ex. 3. A line from Hanover to Windsor, ten miles, has a 
record of 130 ohms. A certain measurement made at Hano- 
ver gave only 100, but when insulated at Windsor, it gave 
200. How for from Hanover was the fault? 

4. A line from Oberlin to Wellington, 8 miles has a record 
of 126 ohms, or 14 per mile. One measurement, however, 
gave 100 ohms, with the ground wire on at Wellington or 
1=56 with it off. Locate the fault? 

Ex. 5. A merchant in New York has a private line run- 
ning 8 miles to his country residence. The average resist- 
ance is \2\ ohms per mile. A test, however, gives Si. 2^ 



112 MANUAL OF TELEGRHPHY. 

ohms, while the test for high resistance (insulated) gives the 
same. Where is the fault? What is its nature? 

In this case, as the high resistance only equals that obtained 
with the ground wire on, it is evident there is a totr.l escape, 
or ground, at 81.25 onms distance: this divided by 12.5 gives 
6.5 miles, the A us. 

Ex. 5. An organ builder in Boston has a wire irom his 
sales-room in that city to his factory at Cambridge, 10 miles 
out. The recorded resistance is 130. A test at Boston gives 
but 100. The insulated test gives also 100. Where is the 
fault? 



CHAPTER X. 
OOnSTIDTJCTI-VIT'-Y". 






1. What is the meaning of this term? 

Conductivity is the opposite, or the reciprocal, of resistance. 
A wire which has twice the resistance ot another has but 
half the conductivity, and vice versa. 

2. Give an example. 

From Table III., appendix, we find that silver has five times 
the conductivity of brass. We infer that a brass wire of a 
given size will offer five times as much resistance as a silver 
wire of the same size and length. 

Illustrate by two iron wires. 

One mile of No. 9 galvanized iron wire offers a resistance 
of 16 ohmsr No. 4 offers 7,8 ohms. No. 4 has, therefore, 
a conductivity nearly twice as great as No. 9. 

4. Does conductivity depend on surface or weight? 

In wires of the same metal and sa?ne length, conductivity 
varies as the vjcight. If the length varies then conductivity 
varies as weight divided by the square of the length, or C 00 ~, - 

5. How long a Xo. 4 wire will have the same conductivity as a mile of No. '.) 
wire? 

According to the answer of question first, conductivity is 



OF CONDUCTIVITY, US 

inversely as resistance. The length should, therefore, be 16 
-*■ 7,8, or 2.05 miles. 

6. If several circuits drain one battery how is their Joint conductivity found? 
The joint conductivity of several circuits is found by adding 

W 

together the fractions, ^r Which express the conductivity 

of each. 

?. How do heat and cold effect conductivity. 

The colder a wire is the better its conducting power. Heat 
increases resista?zce at nearly a uniform rate at ordinary tem- 
peratures. At the melting point it is enormously increased. 

8. Compare Silver and Mercury. 

Mercury, which is liquid at ordinary temperatures has a 
conductivity of only 1.6, silver being rated at 100. Mercury 
solidifies at 40 below zero, and at that point suddenly attains 
a much higher conducting power. 

9. What is said of the conductivity of alloys? 

The conductivity of alloys is much less than the joint con- 
ductivity of the metals which compose them. 

10. Of what are resistance coils made? 

Resistance coils are commonly of German silver, which has 
a very high resistance and is less affected by changes of tem- 
perature than most metals or alloys. 

Standard coils are, however, made of an alloy of silver one 
part and platinum two. 

11. How much are the common coils affected by heat and cold? (Table 4, ap= 
pendix.) 

A german silver wire which has 10 ohms resistance at 32 ° 
Farenheit will have at 70 , which is the ordinary temperature 
of the office, a resistance of 10.812 ohms. 

12. How is this made out from table 4 ?. 

The right hand column of the table gives .024 as the varia- 
tion for each degree of temperature. From 32 to 70 degrees 
is a change of 32 degrees, so that 38X.024 = .Si 2 is to be 
added to 10 giving 10.812. 

13. What standard of conductivity is commonly used? 

Pure copper (99.9) is usually put at 100 and used as the 
standard in place of silver. 

14. What is the relative conductivity of the best commercial copper? 
Wire made of carefully selected copper, such as is used for 

7 



114 MANUAL OF TELEGRAPHY. 

relays, usually has about 90 per cent of the conductive power 
of pure copper. A little alloy of lead or arsenic greatly 
reduces its value for telegraphic purposes, so that ordinary 
copper wire has not much above 40 per cent the conductivity 
of the pure metal. 

15. How is a standard found? or how do we get a basis for comparison? 

By experiment with the purest copper, a single pound of 
metal drawn to the length of one nautical mile (2029 yards) 
of wire, has a resistance of r 155.5 ohms at 60 farenheit. 

Xow if the wire weighs 10 lbs. to the mile its resistance is 
one tenth as great, and so in proportion for any other weight. 

10. What small unit is tahen for the standard of conductivity ? 

One inch of pure copper wire weighing "one grain is the 
standard wire. 

17. Give its resistance and its conductivity? 

The resistance of this unit is .001516 ohms. Its conductiv- 
ity by the formula -^jir = -j^^r 

18. From this how do we deduce the conductivity of any other pure copper 
wire? 

Rule I. The conductivity of pure copper wire of any size 
and length will be weight in grains divided by .001516 ohms, 
and by the square of the length in inches. 

10. How can we also Had the resistance of pure copper wire? 

Since resistance is the reciprocal of conductivity, rule 1st., 
inverted gives resistance. Hence, 

Rule II. The resistance of pure copper wire of any length 

or thickness is eqital to the -product of .001516 by the square of 

its length in inches, divided by its weight ingrains. 

L*X.0Q1510 ' 

Inat is R = — — 

\Y 

£0, In rule 1st. Why divide by the square of the length? 

Suppose the wire one inch long and of one grain weight, 
to be stretched to two inches. Xow its resistance from length 
alone is twice as great as before. But it is also only half as 
large, which fact again doubles its resistance. In other words 
each inch of it will now have twice the resistance it had at 
first and there are two inches. It has, therefore four times its 

NOTE.— 1 pound Avoirdupois = TJCO grains Troy. 
8* 



OF CONDUCTIVITY, 115 

original resistance. If stretched to three inches its resistance 
would be nine times as great 

21. In selecting wire for a relay or galvanometer how is it tested? 

Rule III. To test a wire. ist. Find its resistance by a gal- 
vano77ieter and resistance coil. 

2d. Find what its resistance should be if it %vcre of pure 
copper, by rule II. 

3d. Divide the first of these results by the second. The 
qvotient is the conductivity. 

Ex. 1. A helix containing 5000 feet of copper wire weighed 
4 pounds. Its resistance was 22 ohms, what was its conduc- 
tivity? Ans., .8S6. 

Ex. 2. A certain relay contains 1000 feet of copper wire 
whose weight is 3-7 of a pound. The galvanometer gave its 
resistance at 8.084 ohms. What is its conductivity? 

Ans., 75. 

Ex. 3. A helix was purchased for a relay' Its wire was 
500 feet long and weighed 2 and 2-7 ounces. Its resistance 
was 36.64. What was its conductivity? A ns., 50 per cent. 

2. Testing a Line Wpre for Conductivity.— 1. On what basis should aline 
Wire be teste*.. V • 

As line wires arc almost universally made of galvanized 
iron, a convenient basis is the one already given; 16 ohms 
resistance for one mile of No 9 wire, or 13.5 ohms for No. 7 
wire, and J. 8 ohms for No. 4. Or, copper may be still used 
as a standard; the resistance of the best galvanized iron being 
taken at one-seventh that of pure copper. 

2. Describe the teat? 

A convenient section of from 10 to 20 miles examined with 
ground wires on, but all instruments at intermediate stations 
are detached. The finest weather is to be selected and the 
mean of many observations recorded. 

3. Why are so short lengths taken? 

In a long section faults of an opposite kind might occur, e. 
g., an escape in one place and a bad connection in another 
and the resistance, might appear to be right. Examination of 
short section is -more likely to detect all faults. 

4. Suppose No. 9 wire gives just 1G ohms per mile on a section twenty miles 
long, what would be inferred? 



U6 MANUAL OP TELEGRAPHY. 

No telegraph line will give the full resistance belonging to 
the wire unless there are bad joints. We should suspect a 
line that is too perfect! 

5, What is a good average conductivity? 

Ninety per cent is regarded as a good normal average oil 
well insulated lines in dry weather. This would be 14 ohms 
per mile on No. 9 wire. If a higher average can be secured 
by perfecting the insulation, so much the better. 
7. What rule will apply to all lines? 

Rule IV. The resistance of each mile of galvanized iron 
tuire at 60 degrees Fahr. is found with sufficient exactness by 
dividing 360000 ohms by the square of the diameter. The 
diameter being given in mils i. e. thousandths of an inch. 

3. Testing the Instruments.— -1. How is this test made? 

All instruments should be tested when new and perfect 
and the resistance and percent of conductivity recorded. At 
any subsequent examination, after the naked line is tested, 
the instruments one at a time may be put in the circuit and 
the No. of ohms unplugged in the rheostat on their account 
will show whether they are in perfect order or not. Where 
it is practicable they should be frequently tested independ- 
ently of the line. 

2. What rule is used in these tests? 

As the instruments are all made of insulated copper wire, 
Rule III, in this chapter, will give their conductivity. Their 
least resistance being known, however, mere inspection will 
give their conductivity. 

3. Illustrate by a case? 

Ex. i. A relay when purchased had a conductivity of 90 
per cent, with a resistance of 8 ohms. A subsequent test 
showed 12 ohms. This at once reveals that its conductivity is 

Q 

or .7; of what it should be. 

12 ■ J 

4. How near to pure copper is it now? 

It has now 75 per cent ot 90 per cent, which is 67^ per 
cent of the conductivity of pure copper. 

Ex. 2. A sounder, when perfect, had 5 ohms resistance, its 
conductivity being. 91 that of pure copper. After continued 
use it had a resistance of 7 ohms; what was the probable 
defect? What was its conductivity? 



OF CONDUCTIVITY. 117 

Ans., .65 that of pure copper, or .7 14 of what it should be. 

Ex. 3. A relay with a conducting power of 90 per cent 
had 7 ohms resistance. A subsequet test showed but 6 ohms 
What was the probable defect? What was its conductivity? 

Ans., to last. Its apparent conductivity is now 1.25 that of 
pure copper, an absurdity which the nature of the fault will 
explain. 

Ex. 4. At 60 degrees Fahr. what should be the resistance 
per mile of a line wire whose diameter is 300 mils? See rule 
IV. Ans. 4 ohms. 

Ex. 5. At the same temperature what should be the resist- 
ance per mile of a line wire whose diameter is 120 mils. 

Ans. 25 ohms. 

Ex. 6. What is the proper resistance of a line wire whose 
diameter is 400 mils, when the temperature is 90 Fahr. The 
resistance of iron changes .35 per cent for each degree of 
temperature. 

Ex. 7. What is the proper resistance of the same wire at 16 
degrees Fahr. 



CHAPTER XII. 

THE LINE. 
. , -#_. 

1. What are tlie essential parts of the telegraph line? 

Outside the office the line consists of three essential parts, 
the poles, the insulcitoi's and the wire. 

% What material should he vised for poles? 

Thoroughly seasoned wood of oak cedar, hemlock or 
spruce is best. They should be pealed and seasoned under 
cover if possible, and always separated by sticks while dry- 
ing- 

3. Should the poles be non-conductors? 

The poles need not be insulaters. Iron would be a good 
material. The English wind a wire down the pole to the 
ground to prevent "ciphering" or leakage of current from 
one wire to another. An escape is less annoying than a 
cross. 

4. What if seasoned poles cannot be had? 

In case green poles only can be found, they should be 
stripped of their bark and the lower ends baked or charred, 
but never covered with tar, as this confines the s^p and 
hastens decay. 

5. How should they be set? 

The butt ends should be charred six feet, and then set per- 
pendicularly in the ground, not less than five feet deep, and 
as near a straight line as possible, to prevent strain. In 
curves the pole should always lean against the strain of the 
wire. If possible, keep the line on the inside of railway 
curves, both for the sake of economy and safety. 

G. Is it better to paint the poles? 

If the poles are thoroughly seasoned through, it is best to 
paint them, but it requires nearly a year to accomplish this. 
Generally poles had better stand a few months before paint- 
ing. 

7. What, is the best size? 

They should be at least five inches in diameter at the top 



OF THE LINE. 119 

and from fifteen to twenty feet in length; according to the 
situation; the taller poles being necessary in low places. 

S. How many poles are required to the mile? 

They are usually set one hundred and seventy-five feet 
apart which requires thirty to the mile, but this varies with 
the quality of the wire and the straightness and level of the 
line. The more crooked and uneven the ground the more 
poles are required. On straight; level lines twenty to 
twenty-five will do. 

1. Insulators and Crossbars.— 1. What size and length are required for 
crossbars. 

The crossbar should be two inches by four, of tough wood, 
the upper edges beveled oft', and long enough to keep the 
wires not less than two feet apart. Three or even four feet 
apart is still better, but this is often an impracticable distance 
where there are many wires on one set of poles. 

2. Why is it better to keep them far apart? , 
Wires near together are very apt to form crosses, and if 

they are less than two feet apart, secondary currents may be 
formed, especially on main lines with large batteries. 
;-}. How are the crossbars fastened? 

The bars are let in to the pole an inch, and bolted through 
or heavily screwed. They should be made so strong as to 
stand the strain when a wire on one side of the pole is down, 
and the balance is thus lost. 

4 What arc the insulators? v 

The insulators are the glass or other insulating projections 
attached to the poles and crossbars to prevent the escape and 
intermingling of currents. 

5. How is insulation in tunnels, or under ground affected? 

Insulation at the points of support merely, is insufficient in 
tunnels and damp places. In such cases the whole wire is 
covered with gutta-percha or vulcanized rubber as ocean 
cables are. 

G. What are tho greatest hindrances to in illation? 

Moisture, soot, or dust deposited on the surfaces of the 
insulators form a conducting medium and occasion leakage, 
ciphering and great waste of power. Especially in the cities 
these causes are usually active. 



120 MANUAL OF TELEGRAPHY. 

7. What is the first requisite in a good insulator? 

The first requisite is of course that it should have a very 
high resistance — infinitely high if possible — glass, porcelain, 
vulcanite, compositions of coal tar, and stoneware saturated 
with parafine are reckoned among the best practical materials 
for this purpose. 

8. What else is to be taken into account in selecting materials? 

1. The surface of the insulator should repel water and the 
material should not be porons so as to absorb moisture. 

2. It should not crack or change by the weather, or from 
the sun's influence. 

3. It should have as great strength as possible, to endure 
either a stretching or a crushing strain. 

9. How do the materials mentioned compare in these respects? 
Vulcanite is the best insulator, is the strongest and repels 

water, but does not endure the weather so well as glass, or 
the composition. Glass is most used, though weak and not 
repelling water. Perhaps the last mentioned combines the 
the most of these excellencies. (Q. 7-) 

10. What form and size is best? 

The diameter should be as small as strength will allow, and 
the length should be as great as convenient, because the 
resistance is increased by both these circumstances. 

The form (Fig. 55) should be such as to Fig. ss. 

allow the least deposit of snow or rain or 
dust, and yet to admit of secure fastening to 
the wire and supporting pin. 

11. How is the glass sometimes supported? 

In the Wade insulater the glass is pro- 
tected by a wooden shield which has been 
thoroughly saturated with hot coal tar. 
The glass is cemented by a non-conducting 
substance. 

12. How is hard rubber used? 
Hard rubber or vulcanite is sometimes 

used to cover an iron hook and then the whole set into a 
cavity in the lower side of a crossbar. Glass is sometimes 
used in the same way. 

13. How is the paraflinc insulation secured? 




OF THE LINE. 



121 




In Brooks' stoneware insulator, (Fig. 
56) a stone cap is saturated with para- 
ffine and screwed to an iron pin which 
is itself screwed into the crossbar or 
bent up and screwed directly into the 
post. This affords a far better insula- 
tion than any glass cap, and is cheap. 

14. What precautions are necessary in fastening 
the insulatera? 

If the bracket is used, its shoulder 
should be cut away, leaving an edge on 
the upper side so that rain will not spatter up under the 
insulator, and snow will not accumulate. The edge of the 
insulator must be at a considerable interval from the bracket, 
else in a rain storm continuous connection with the ground is 
formed by the water. 

15. How is it on a crossbar? 

The upper surface of the crossbar is made sharp for a like 
reason unless suspension insulators are used. 

16. To what liabilities is the insulator subject? 

The wind sometimes lifts the wire and the insulator is car- 
ried off the pin. In crossing a valley where the posts are 
not up to the general level, the strain of the wire, especially 
in cold weather will often lift them in the same way. 

17. How is this prevented? 

The stoneware insulator (Fig. 56) is not liable to these 
accidents unless the strain is so great as to break it. If other 
insulators are used, a few suspension hooks which are 
attached below the crossbar should be provided. 

2, The Line Wire.—l. What are the desirable qualities in the line wire? 

A line wire should combine strength, lightness and high 
conductivity as far as those are compatible. Cost is of course 
an important element; but a slight difference of cost will not 
compensate for a large sacrifice of these qualities. 

2. What metal combines them best? 

By a glance at Table III in the Appendix it will be seen 
that steel and zinc though far inferior to copper are each 
better than iron. Coating iron or steel with zinc is different 
from making an alloy and rather increases conductivity} 



122 MANUAL OF TELEGRAPHY. 

while protecting from rust. Coating with copper will do 
the same in a higher degree. Steel covered with copper is 
best. 

3. How does the latter compare with galvanized iron? 

A wire of steel, copper sheathed, of Xo. 14 size, has as 
high conductivity as Xo. S galvanized iron, and weighs 
only about one-fourth as much. It has greater tensile 
strength than the iron and costs less, 

4. Why is it not more used? 

It needs only to be known to be more extensively em- 
ployed. 

5. Is it good economy to use small wire? 

By using large wire, and consequently high conductivity, 
a line may be worked with fewer cells; and the tension being 
less, there is less loss from escape, and every instrument 
works more freely. It would be far better economy to use a 
steel wire as large as Xo. 10 than a smaller size. 

G. How is the wire protected in cities? 

On account of the gas from burning coal and other causes 
the wire used in cities corrodes easily and should be painted 
before it is put up, especially if galvanized with zinc. 

7. How is the wire attached to the insulator? 

■ The wire should not be bent around the neck of the insula- 
tor as this would crush the glass, but should be laid in the 
grove at one side and fastened by a separate wire. Bending 
the wire abruptly also injures the continuity of its surface 
Fig. 57. and lengthens the line. Some insula - 

j tors require no tie wire; the fasten- 

ing is made by slightly bending the 
line in and out of an inverted T 
shaped hook as in Fig. 57. 
S. How are two wires spliced? 
The wires should nevei be joined by looping together, but 
they should just lap by each other a few inches, and then 
each end should be tightly wrapped around the wire, (Fig. 
58.) and cut close, leaving no loose ends to hook or catch any 
thing. 







OF THE LINE. 
Fig. 88.. 



123 




9. Is the joint then complete? 

No joint is complete till soldered. Rust or wear is sure to 
cause great resistance unless this precaution is taken. 

10. How is the soldering done? 

A solution of chloride of zinc with a little muriatic acid, is 
put on thj joints till it wets all parts of it. The whole should 
then be heated over a coal furnace till it is at the melting 
point of the solder, a slender rod of solder is then rubbed along 
the joint which will be instantly and thoroughly filled with it. 

H. What precaution is to b3 observed? 

The wire should not be overheated, but should be felt of 
by touching it with the solder as it approaches the proper 
temperature. If copper and iron are connected the chloride 
of zinc should be washed off and the wire protected with var- 
nish to prevent galvanic action between the metals. 

3. Strain oftJie Wires.— I. How nearly straight should the wires be drawn? 

In Culley's Hand-book, the proper dip for a span of So 
yards, in mild weather, is given as iS inches below the level. 

Fig. 89. 

S B 



A 



V 




That is V S, called the versine, (in Fig. 59,) is iS inches 
when A B is So yards; with No. 8 wire this causes a strain of 
420 lbs, the breaking strain being 1300. 

2. Suppose the span is less than 8) yards? 

The same wire with a span of 60 yards should have a versine 
of 10^ inches. It is found as follows: Putting L for length of 
span, and V for versine, the rule is, L 3 : I 2, : : V : v. Tak- 
ing the numbers given we have So 2 : 60" : : 18 : 10^. 

3. Does the weight of a wire make a difference? 

If the wires are of different sizes the strain varies directly 

l 3 Xw 
v 



as the weight and inversely as the versine. Or S 00 



124 MANUAL OF TELEGRAPHY. 

and the strain should never exceed one-third the breaking 
strain. (See Table IV, Appendix.) 

4. Where is the strain greatest? 

The strain is greatest at the point of suspension, but only by 
the weight of a wire equal in length to the versine which is 
unimportant. 

5. What rule will give the proper dip for good wire of any weight for any 
span? 

RULE III. Square the span expressed in yards, and 
multiply this by the number of civts. in one 77iilc of the wire. 
Divide by one-third the breaking strain, and by 31.43. 

6. Give Clark's formulas for the comparison of strain and dip. 

Clark's formulas are, strain = D1 , . . 
and dl P = 3L43X^ 



m • ^ 



CHAPTER XIII. 

OCEAN CABLES. 



1. How are the ocean cables worked? 

Owing to the enormous lenght of the cable, sufficient 
power cannot well be transmitted to work a Morse register, 
the mode therefore adopted is to operate a galvanometer 
needle, and from the movements of the needle signals are 
received. 

2. What kind of a galvanometer is used? 

A very delicate galvnaometer devised by Thompson is 
used. It consists of a very light magnet, half an inch long 
suspended by the thinnest possible platinum wire within a 
circular helix of many thousand convolutions. The magnet is 
polished on one side and a ray of light falling on the polished 
surface, is reflected upon a screen twelve feet distant. The 
slightest motion of the needle appears thus greatly magnified 
on the screen. 



OF OCEAN CABLES. 105 

How is the motion interpreted? 

The Morse alphabet is used and its signals are inferred 
as follows: When no current is passing the ray of light 
settles to a zero mark on the screen. When a current flows 
through in one direction the ray deflects to the left, and is 
interpreted as a dot, when the current is drawn backward 
through the coil the needle veers to the right of zero, and this 
is a dash, long or short, according to the time it remains. 
The needle at zero is a space, whose length is determined in 
the same way. ; 

4. How is the current drawn backward? 

To understand the return of the current it must be borne 
in mind that the cable itself is like an immense Leyden jar, 
the wire constituting the inside coating and the water the out- 
side. In sending a signal the cable has to be chaiged up to 
the potential of the battery. To produce a return current it 
is only necessary to partially discharge the cable. 

Fig. eo. 








5. Explain the operation of the condenser. 

The battery B at the sending station is connected with the 
cable by the back contact of the key at K. The cable is there- 
fore kept permanently charged. But upon depressing the key 
making contact at I the cable is connected with the earth at 
E. To effect a complete discharge requires a considerable in- 
terval of time. At the receiving end is the reflecting galva- 
nometer G. and beyond it is the condenser C. At the cable 
divides and one branch goes through the powerful rheostat R 
and thence to the ground. This gives a constant but very 



126 MANUAL OF TLLEGEAPE1. 

small escape, reducing the tension in the galvanometer and 
condenser a very little below that of the cable. 

Xow the first signal must always be made by momentarily 
depressing the key which reduces the tension of the cable a 
little below that of the condenser, when a flow of the cur 
rent backward through the galvanometer takes place turning 
the reflecting magnet, or point of light to the left of zero. On 
raising the key, back contact is restored, and the potential of 
the cable being highest again, the current passes through the 
galvanometer, turning the magnet in the opposite direction, 
and charging the condenser as before. 
G. What are the advantages of thi&jnethod? 

By this method the cable is' never .entirely discharged and 
the balance between the potential of the condenser and that 
of the cable being very slight", a. current may be readily made 
to pass either* Way thrpug the. galvanometer. 

"7. Afwhat rate are signals sent? 

By this mock)' frorn fifteen to twenty words a minute may 
be sent by an expert operator. (Appendix D). 

8. How does this compare "with messages by airlines? 

The number of words by air lines has in rare instances 
averaged forty to forty-five words per minute, when receiv- 
ed by sound. 

1. Faults hi the Cable.— 1. By what modes are faults in the cable located? 

The methods for locating faults are the same as for air lines: 

ist — By direct measurement, 

2d — By Blavier's method. 

3d — By the loop test when there are two lines adjacent. 

2. What method is practiced while the cable is beicg laid? 

During the process of laying the cable the battery is on 
ship-board and a current is passing through the whole cable, 
both the portion coiled in the ship and the part already laid. 
A galvanometer is placed between the battery and cable so 
that any change in conductivity would instantly be revealed- 
At the shore end a very high resistance is placed between the 
cable and the galvanometer, while beyond the galvanometr 
the wire is grounded. The high resistance allows a feeble 
current to traverse the galvanometer, keeping its needle per- 
manently but slightly deflected. The resistance is necessary 






OF OCEAN CABLES. 127 

iii order that the tension produced on shipboard may remain 
nearly static in the cable. Now the slightest leak in the cable 
produced on lowering it, would instantly reduce the potential 
at that point, and the galvanometers on shipboard and shore 
would both be affected by a current setting toward the leak. 

3. How is the close watching relieved? 

Every fifteen minutes the ship reverses the battery and the 
effect being observed on shore assures the continuity of the 
cable to that moment. Other relief is only made by a change 
of observers. 

4. If a fault occurs how i> it located? 

The tension on shore, on the sea side of the high resistance, 
is allowed to charge a condenser which remains attached to 
the cable for ten seconds. The condenser is then suddenly 
discharged through a separate galvanometer, into the earth, 
and the tension it had is thus measured, and the result is com- 
municated to the ship. Knowing the tension before and after 
the fault, the operator on ship-board can calculate its pre- 
cise position. * 

5. If the core of the eahle breaks, how is the break located? 

During the manufacture of the cable a record is made of the 
quantity of static electricity that each mile of it can contain. 
If it break within the gutta percha, still remaining insulated, 
it is only necessary to divide the number of farads which -the 
broken section can now contain by the average number of 
farads which each mile contains and the quotient is the dis- 
tance in miles. 

0. How do they ascertain the capacity? 

A condenser of known capacity is discharged through the 
galvanometer and the deflection noted. Then the cable is 
discharged through the same galvanometer and the amount 
of deflection it makes is compared with the other. 
7. How arc cable joints tested? 

The cable joint is immersed in a trough of water and a bat- 
tery is connected with one end of it, the other being insulated 
by standing out of water. The trough is insulated and if 

■ NOTE. Clark's formula for tin's calculation is T— t : t— s : : R : x, where 
T and t are the tensions on shipboard each side of the resistance coils, 6 = the 
resistance of the shore end of the cable, and R the whole resistance before the 
fault occurred. X is t lie dis tance of the fault from the ship. 



JgB MANUAL OF TELEGRAPHY. 

there is any leakage from the cable it is allowed to aCCumu* 
late in a condenser for a minute or other definite unit of time* 
The condenser is then suddenly discharged through a galva- 
nometer and the amount of leakage is measured. 

This must not exceed that from the same length of perfect 
cable. 

8. How can the ship communicate with the shore amid all these tests? 

A separate condenser is employed, and by a sudden dis- 
charge of it, although the cable seems fully charged, yet pul- 
sations can be sent through it, which act on the galvanome- 
ter needle at the receiving end. 

9. How may a cable he minutely examined throughout its length? 

A mile or more of the cable is wound on a drum and a pow- 
erful battery connected with one end, the other being insul- 
ated. The cable is then slowly wound off onto another drum, 
a few inches of it always passing through a basin of water. 
A wire from the water leads through a delicate galvanome- 
ter and thence back to the negative pole of the battery. The 
slightest escape will thus be detected. 

10. Is the perfect cable tree from all leakage? 

The best cable shows so much escape by this examination 
that a provision is made for resisting it. A wet thread is used 
instead of wire from the basin to the galvanometer, and only 
the excess of deflection from a fault is noticed. 



CHAPTER XIV. 
OFFICES AND CONNECTIONS. 



Wires entering, or in an office should not touch each other, 
or touch a communicating metal, though they are supposed to 
be thoroughly insulated. The insulation may be burned off 
by lightning, or some accident may abrade it. Nor should 
the office wire be spliced if it can be avoided, but if spliced 
it should be soldered. The line wire should be well support- 
ed by an insulator at the point where it enters the office and 
the entrance should be made through a glass or hard rubber 
tube inclining downward on the outside to keep out rain. 
Inside the office the line wire should be screwed or soldered 
to a binding post, from which the copper wires of the instru- 
ments lead off to their respective localities. 

Fig. 63. 




(> 



,-©00030 



^00"- 

LB 




Mli 







Fig. 63 represents the relative situation of batteries and 
instruments at a terminal station. 



1 30 



MANUAL OF TELEGRAPHY, 



The m?»in line enters at L, passes through the lightning 
arrester at A, thence to the relay R, through the binding 
post i, thence from the relay through the binding post 2 to 
the key, K, from which it passes through the main battery 
M. B., to the ground at G. A ground wire also passes 
directly from the lightning arrester to the ground. The con- 
nections of the main circuit are represented by the continu- 
ous line, the local circuit by the dotted line. The latter passes 
from the positive pole of local battery L. B., to the relay 
armature through binding screw 4, thence through 3 to the 
sounder Q^, thence back to the local batteiy. 

Fig. 64. 



A 

cD)Y(^ 

a 



n@ 



or u 






Q 



LB 




very 



The arrangement of instruments and batteries at a 
station is shown in Fig. 64. 

The course of the line is from L, through the lightning 
arrester A, to the relay R, by way of the binding post 1, 
thence through 2 to the key through the second lightning 
arrester to the line L'. 

At S is a "cut out," a button switch, which may be so 
turned that the current will not enter the relay, but will make 
the short loop L. S. U. The ordinary plug switch may be 
made to answer the same purpose, 

The ground-switch G. W. is so arranged that either side of 
the line may be connected with the earth. It is used only in 
detecting escapes, or when called for by the main office for 
any purpose. 

9 



APPENDIX 



A. — Clark's Double-shunt Galvanometer* is a very excel- 
lent form of the differential instrument. That is, it is wound 
with two wires designed to carry currents in opposite direc- 
tions about the needle. One of these circuits extends from A 
to B, (Fig. 60) the other from C to D. These wires are both 
adjusted to have the same electrical resistance and also to have 
the same effect on the needle, so that when a battery is con- 
nected to the two central terminals B. and C. the current 

Fig. 61. 




divides itself into two equal portions; one flowing from B to 



Clark's Elementary Treatise,/. 47 



132 MANUAL OF TELEGRAPHY. 

A and tending to deflect the needle to the right and the other 
from C to D, deflecting it to the leit; but since the quantities 
and forces are precisely equal the needle remains at rest. If 
equal resistances are added on each side of the galvanometer 
the needle still remains motionless, but if unequal resistances 
be added, more electricity Hows to that side which has the 
lesser resistance and the needle is deflected tojdiat side. The 
peculiarity of the instrument consists in the addition ot a 
shunt or derived circuit to each half of the galvanometer. 
These shunts are marked on the instrument '"shunt i-ioo." 
They are short wires having a resistance equal to one ninety- 
ninth that of the half coil, and when thrown into the circuit 
by the insertion of the plug, ninety-nine one-hundredths of 
the current pass through the shunts, only one one-hundredth 
traversing the galvanometer. The instrument is supplied 
with resistance coils varying from one to ten thousand ohms. 

B. — The internal resistance of different batteries as ascer- 
tained by the nice experiments of Dr. Clark are as follows: 

A. Grove's cell oilers the least resistance, being usually 
below i ohm per pint cell. 



Darnell's from 5 to 10 ohm 



lS. 



Smee's below 1 ohm, which greatly increases, however, 
with the deposition of hydrogen bubbles. 

Table first gives appoximately, also, the comparative elec- 
tromotive force of the different batteries. 

0. — The Electro-static Capacity of an insulated body is the 
number of farads it will receive with a unit, or volt, of force. A 
Leyden jar, for example, may have its inner coating connected 
with the positive pole of a single Daniell's cell, and its outer 
coating with the earth. The negative pole of the battery goes 
also to the earth. The jar will now be charged up to its elec- 
tro-static capacity, and if the battery be detached, the dis- 
charge may be affected through a galvanometer. The force 
is impulsive and the distance which the needle moves, com 
pared with that which one farad of quantity will move it. 
will give the capacity of the jar. 

The outer coating of the jar all this time exhibits no tension 
whatever, its force being disguised. 



A^PENfilX. 133 

The Capacity of the jar varies directly as the amount of 
coated inner surface and inversely as the thickness of the 
glass. 

D. — Measurement of force. In determining the electro-motive 
force of batteries it is implied in the answer to question 2, p. 
103, that the needle point of the galvanometer will move over 
an arc exactly proportional to the force. This can be taken 
as true only when the movement is confined to a small arc of 
perhaps 1 ^ degree or less, /. c. while the needle remains 
almost parallel with the wires of the helix, unless the force is 
a mere impulse. 

Various devices have been employed to obviate this defect 
ot the galvanometer. One form of the instrument has the 
needle so suspended that in turning, it shall twist an exceed- 
ingly fine platinum wire, which will thus offer a constantly 
increasing resistance to its motion. The graduated circle is 
detached so that it can be set in any position, and the helix 
can be revolved on a vertical axis. As soon as the needle is 
deflected from any cause, the helix is to be turned with it; 
thus the force is exactly measured by the number of degrees. 
For many purposes this instrument is not available. A more 
skilful device is the "tangent galvanometer.' , In this, the law 
of the resolution of forces is applied, the needle being always 
found in the direction of the resultant. The radius of the 
circle, or half the length of the needle, represents the force 
which tends to hold it in its place, while the tangent of the 
arc it describes, represents the disturbing force of the current. 
The needle when deflected, will occupy the position of the 
secant of the arc, pointing always to the extremity of the 
tangent, which may thus be read off on a scale attached, or 
may be more accurately calculated from a table of tangents. 

A simple method much used in measuring the tension and 
the capacity of a cable is to note the swing of the needle from 
an instantaneous discharge as described above for the Leyden 
jar. 

By this method also, in connection with shunts and con- 
densers the tension of a large battery may be readily deter- 
mined. 



134 MANUAL OF TELEGRAPHY. 

E. — Spontaneous Discharge of the Cable. When the batteries 
are detached, the cable gradually loses its tension by what 
is called leakage. This is probably occasioned not by defects 
or openings in the gutta-percha covering, but by the polariza- 
tion of the dielectric, which gradually unites the positive of 
the core with the induced negative of the surrounding water. 
In other words the gutta-percha is a slow conductor of elec- 
tricity. 

The ratio of this loss or leakage does not vary with the 
intensity of the charge, but the tension falls from any height 
at the rate of about 7 per cent of the whole amount present, 
each minute. That is, seven per cent of the whole charge i.- 
lost the first minute, seven per cent of the remainder the next 
minute, and so on indefinitely. It is easy by successive sub- 
tractions of seven per cent to find how many minutes it takes 
to fall one-half. The higher the tension the longer it takes 
and thus the battery jDower may be known. 

Latimer Clark institutes direct comparison of the cable ten- 
sion with that of separate condensers, which are severally 
charged to the whole tension, 90 per cent, So per cent, 70 
per cent and so on as far as is convenient. At suitable inter- 
vals of time the cable on one side of a galvanometer and the 
condenser on the other are connected through it by the sim- 
ple movement of a key. If the cable and condenser are alike 
no deflection of the needle takes place. If the cable is either 
above or below the tension of the condenser a slight corres- 
ponding deflection will result. 

G. — The subject of electric light is one of great interest 
though not connected with telegraphy. The simplest form 
of the apparatus for producing the light is exhibited in 
Fig. 65. 

S is a supporting standard having two brass balls separated 
by a glass rod. Through the upper ball the current passes 
from A to a brass rod which terminates at C in a carbon point. 
This rod is moveable up and down by the handle H. At 
G is a second carbon point which is connected with the 
wire N. Suppose A and N to be connected with the battery. 



APPENDIX. 



135 



Fig. 65. t he handle H is pushed down till the 

carbon points touch. The current is 
thus established, and as the carbon is a 
poor conductor, and small at the junc- 
tion, a great resistance is offered at that 
point, and an intense heat accompanied 
by light of dazzling brilliancy is wit- 
nessed. 

The points may now be withdrawn a 
^ short distance from each other, to in- 
crease the resistance, when an "electric 
arch" of wonderful splendor plays be- 
■" tween the points. 

The electric lamp is a contrivance of 
clock-work by which the carbon points, 
as they waste away, are kept at a uni- 
form distance from each other. 
-The development of electricity by heat is 
beautifully shown by the apparatus exhibited 
in Figs. 66 and 67. A bundle of bars of anti- 
mony and bismuth are soldered together at 
alternate ends as in Fig. 66, and the outside 
plates, one of antimony and the other of bismuth terminate 
each in a wire, on applying a gentle heat to one end of the 
bundle, a current of electricity is at once set in motion 
from one metal to the other. 

Fi s- 67. A compact bundle of 

such plates is seen at T 
in Fig. 6 1 ], and the wire 
terminals are connected 
with a galvanometer. On 
turning the cap, which 
^-''Ji covers the end remote 

$35£- : I I from the galvanometer, 
. -% .. . even the warmth of the 
.-^V; ; > hand held several feet 






distant is enough to cause a visible deflection of the needle 
Such a bundle is called a thermopile and is one of the most 



136 



MANUAL OF TELEGRAPHY. 




sensitive forms of thermometer ever devised. Any current 
of heated air excites electric action. 

I. The Automatic Telegraph.— The object of this inven- 
Flg - 62 - tion is co enable any 

number of operators 
to receive messages 
from customers and 
by a certain arrange- 
ment to send all 
these by one special 
operator with a ra- 
pidity far surpass- 
ing anything hither- 
to known, as rapid- 
ly ly for example as 
they could possibly 
be articulated with 
the organs of speech. 

The invention is in three distinct parts. The first is a stamp- 
ing machine, which cuts the message entirely through a strip 
of paper which has been prepared with paraffine or other 
substance to render it a non-conductor. 

The Machine consists of a box containing a number of cyl- 
indrical steel rods of the same diameter as that of the holes to 
be punched and lying parallel in groves. To represent a 
dash, three round holes are punched, one of which is out of 
line with the two adjoining, as seen in Fig. 6*-* The number 
of rods equals that required by the longest let'er. A key- 
board in front of the box has the twentv-six letters of the 
alphabet and the other necessary characters scverallv printed 
on the respective keys. On striking any key with the lin- 
ger, the rods necessary to stamp in the Morse character the 
letter printed on it, are driven out a short distance from the 
box and are thus made to perforate the paper. Xo matter 
how complicated the letter, a single touch of the key prints 
it perfectly. The return of the key to its place hitches the 
paper along exactly enough to make a letter-space and a blank 
key struck at the end of a word gives it an additional motion 



APPENDIX 137 

equal to a Word- space. The operator spells the word men- 
tally as he touches the key for each letter, and pronounces it 
on the blank. By this machine the message can be stamped 
in the Morse character nearly twice as quickly as it can be 
written in ordinary scrip with the pen. 

The next part of the Invention is the transmitter. This con- 
sists of a grooved roller two or three inches in diameter over 
which the perforated paper is made to pass, Fig. 63U- 

This roller has metallic connection with the positive poles 
of the battery. Above the paper are two small thin wheels, 
which stand exactly over the lines of holes, and which are con- 
nected with the line wire. Now at whatever rate of speed 
the paper is drawn under these small wheels itis evident that 
when either of them runs into one of the holes of the paper 
it will reach through and make contact between the line and 
the battery thus transmitting a dot to the other terminus of 
the line. To make a dash, the hole which is out of the 
main line of the perforations is made so large that its wheel 
enters it before the other wheel is out of its hole and contin- 
ues contact till the other enters a second hole. This contact 
is maintained as long as is desired, and it is obvious that the 
paper may be drawn through with a rapidity limited only 
by the receiving capacity at the other end of the line. 

The third part of the invention is the receiver. This con- 
sists of a strip of paper so prepared as to be a conductor of 
electricity and having in it such chemical ingredients that the 
passage of a current through it will turn the paper black at 
that point. This strip of paper is drawn over a metallic 
pully suspended much as the larger wheel of the transmitter 
is, and which communicates with the negative pole of the 
battery or with the ground. Above the paper instead of two 
wheels as in the transmitter, there is a single steel needle 
point connected with the line. \\ nen, therefore, a dot is trans- 
mitted the current passes down flie needle and penetrates the 
paper leaving a small black stain, and when the contact is 
kept up by the two small wheels of the transmitter, a dash is 
stained on the paper. The paper is drawn through at about 
the same rate as the perforated paper at the sending station, 



138 MANUAL OF TELEGRAPHY. 

the necessary velocity being agreed upon or ascertained by 
practice. It is not necessary that they be alike. It is only 
necessary that the receiving paper run oft' fast enough to ren- 
der the message legible. It is claimed that by this invention 
one wire will do the transmitting of five or six stamping ma- 
chines and that each of these will prepare a message in one- 
third the time it takes to communicate it in the ordinary way. 
It is not necessary that those who operate the stamping or 
punching machine should know the Morse alphabet though 
the transmitting and receiving operator should of course 
know it and an ordinary key is always at his command, to 
make calls and inquiries. 

J. — It might be inferred from pages 102 and 103 that a 
quantity battery would in no case send a greater quantity 
than a single cell. This, however, depends entirely on the 
amount of resistance offered. The resistance may be so slight 
that a quantity battery, however large, can send away all 
the force generated. If, therefore, we diminish resistance in 
a^ given case we may always increase the quantity until the 
capacity of the conducting wire is fully used, and the electric 
potential will thus be maintained. Whenever the resistance 
of a wire is greater than that of the battery itself a quantity 
battery will not avail to increase the force, but if it is reduced 
and kept below that of the battery, then no matter how many 
cells are joined up for quantity all the electricity generated 
will be sent over the wire. For the production of light, heat 
or magnetism, therefore, short circuits with thick wires are 
best, and very large cells or many joined for quantity may be 
used. 

It is analagous to a large mill dam with a low or slight fall. 
The power will still be great if the flume and buckets are 
very capacious so as to receive all that can be supplied. 

In case of a leak or escape the resistance of a line is dimin- 
ished, and if we wish merely to keep up the original tension 
we have only to increase the quantity by joining up the cells 
into a quantity battery. We can of course supply it by an 
intensity battery, as this will force a greater quantity over the 
wire, but this will also increase the waste which the other 



APPENDIX. 139 



method will not do. An escape constantly tells on a battery 
exhausting its static fund and depressing its tension, below 



what its average should be. 



TEMPERATURE. 

The zero of the Centigrade thermometer is the freezing 
point of water, and ioo° is the boiling point of water. 

Between these two points a Farenheit's thermometer 
makes i8o u . The centigrade decrees are thus nearly twice 
as large as Farenheit's, or in the ratio of 9 to 5. 

To convert centrigrade temperature into Farenheit's, 
multiply by 2, subtract onc-tcnth and add 32. 

Ex. — A centigrade scale shows 20 above zero. 

20X2 = 40, and 40 — 4+32 = 6S°, the temperature by 
Farenheit's scale. 



JOINT RESISTANCE. 

For finding the joint resistance of several branches a rule 
simpler than that given at page 104 is this. Add together 
the reciprocals of the several resistances and the sum will be 
the reciprocal of their joint resistance. Thus suppose three 
branch circuits have a resistance of 30, 60 and So ohms 

respectively ; then jrrr + -tttt- + -g— = -y^— The joint resist- 
once is therefore 16 ohms. 



140 MANUAL OF TELEGRAPHY. 

Table First gives approximately the electro-motive force 
of the batteries in common use. Thus a cell of a Smee's bat- 
tery has only one-fourth the power of a Grove cell. 

Table Second gives the absolute power of different bat- 
teries as nearly as it can be averaged. Thus a single Grove 
cell yields 1.927 volts or nearly 2 volts, while Darnell's yields 
but a trifle more than half as much. 

Ix Table Third silver wire is taken as a standard, and 
the conducting power of a wire of given length and size for 
several metals and alloys is compared with silver. 

For more accurate comparison the resisting power of fluids 
is o-iyen in millions instead of units. 

o 

Table Fourth is an exhibition of the amount ot resistance 
in wires of different metals given in ohms and fractions of an 
ohm. The comparison is made either for a fixed weight per 
foot, or for a fixed diameter and length, the weight varying 
with each substance. This table also gives the per cent, of 
variation for temperature. 

Table Fifth gives the relative sizes and weights of wire. 

Table Sixth gives the different units of measure used in 
telegraphy. 



In the following propositions d repres2nts the diameter in rails (thousandths of 
an inch.) 

IRON. 

1. Specific gravity of bar iron, ... 7.7. 

2. Weight of one cubic foot, 481.25. 

3. Breaking weight of common irons 
Breaking weight of fine drawn wires, per square 

inch section, 40 (a 50 tons. 

(Hard drawn wires, spring temper are toughest.; 

Weight per nautical mile \ii)%) yds.) of iron wire d 3 

Weight per. statute mile (17C0 yds. d- 

72.15ibs 



Diameter of wire weighing n K»s. per statute mile, V 72.15X'' ra * s - 



" " << " " " nautical. " 1 CiLo'JXn mils. 
Conductivity of galvanized iron wire compared with 

pure copper. .14. 

Resistance of galvanized iron per statute mile at GO 

degrees Fahr. ,%0,000 

d' ohm?. 



APPENDIX. 141 

Resistance of No. 8 galvanized iron wire per statute mile 13.5 ohms. 

« « (j* « a c u <* u 15# u 

Increased resistance of iron wire for each degree Fahr. .35. 

Copper, 

Specific gravity of copper wire, 8.8. 

Weight of cubic foot, 550 lbs. 

Bretiking vvt. of copper wire averages to eaeli sqv. inch 17 tons. 

Weight per Statute Mile of any Copper wire = - t - 
Weight of one mile No. 16 Copper wire, about - - 64.5 lbs. 

rv 4. c r- • ■ 1 1 J w ( in oz -^ 

Diameter oi anv Copper wire in inches = — - \— — : — ; 

1 J 2 *& 111 inches. 

Diameter of any Copper wire weighing N / — 

l C24. 1 t -i l/Nx63mila 

pounds per btatute mile 

Resistance per Statute mile of pure Copper 813G1 

wire at 60 ° Fahr. in ohms d 2 mils 

Resistance of No. 16 copper wire per statute mile 19 ohms. 

Resistance in ohms of any pure copper wire 0015104-& 3 - 



b inches long weighing u grains 


11 


TABLE I. 


100 


Bunsen's .... 


08 


Daniel's 


50 


Sniee's 


25 


Woollaston's (copper and zinc in acid) 


46 


M. Davy, sulphate mercury and graphite 

Chloride silver .. ....... 


70 

02 


Chloride lead 


30 



TABLE II. 



Converted into volts the table is : 
Grove's 


as follows : 


1,927 volf 
1 888 " 






Danicll's 


1 > w 
1,079 " 
481 k ' 






Woollaston's 


8S6 " 






1 404 " 


Chloride silver 


1 194 " 


Chloride lead 




578 '■' 



RESISTANCE OF FLUIDS. 

Pure rain water 40,053,723.00 

Water, 12 parts; sulphuric acid, 1 part 1,305,407,00 

Sulphate Copper, 1 pound per gallon 18,450,000,00 

Saturated solution of common salt 3,173,000,00 

of sulphate of zinc 17,330,000,00 

Nitre Acid 30 B 1,(500,000,00 



142 



MANUAL OF TELEGRAPHY. 



TABLE III. 
M. G. Farmers table of the conducting power of materials. 



Silver 


100 


< opper pure 


99.9 


" selected 


.... So to 95 


" commercial 


40 to 70 


Bras? 


20 


Gold 


78 


Zinc 


29 


Steel 


16 


Iron 


15 


Tin 


12.4 


German silver wire 


12 to 16 


Lead 


8.3 


Mercury" 


1.6 


Platinum wire 


6.9 



TABLE IV. 



Resistance Resistance Approxi- 



Xa.me of Metals. 



of wire 1 of wire 1 
foot long, foot Jon"-. 



weighing 
1 grain. 



1 -1000th 

inch in 

ilia meter. 



mate per 
cent, varia- 
tion in re- 
sistance per 
degree tem- 
perature. 



Silver annealed 

" hard drawn 

Copper annealed 

" hard drawn 

Gold annealed 

" hard drawn 

Aluminum annealed 

Zinc pressed 

Platinum annealed 

Iron annealed 

Nickel annealed 

Tin pressed 

Lead pressed , 

Mercury liquid 

Platinum silver alloy, hard or an- 
nealed, used for standard resist- 
ance coils - 

German silver, hard or annealed, 
commonly used for resistance coils 

Gold silver"allo3 T , 2 parts gold, 1 part 
silver, hard or annealed 



0.2214 

2421 

0.2004 

0.2100 

0.5849 

0.5950 

0.00822 

0.5710 

3.536 

1.2425 

1.0785 

1.317 

3.236 

18.740 



4.243 
2.652 
2.391 



9.936 
9.151 
9.718 

9.940 
12.52 
12.74 
17.72 
32.22 
55.09 
59.10 
75.78 
80.36 
119.3) 
600.00 



14S.35 
127.32 

66.10 



0.377 
.209 
.215 
.202 

0.305 



0.365 
.35 



0.365 

0.387 

.04 



0.017 
0.024 
0.065 



APPENDIX, 



143 



TABLE V. 
Table cf the Sizes and Weights of Iron Wire. 



B. W. 

Gauge. 

1 sq. in. 
leire." 
0000 

1 . 


Diam. 

in 
Mils* 


Per Statute Mile. 


Naut 'al 
Mile 


Break 'gj 

weight ; 
at 20 ton 

pr.sq.in- 


Weight 
in lbs. 


Weight 
in cwts. 


Resist 'e 
in ohms 


Weight 
in cwts. 


1000 
454 


17045 

' 13S58 

2854 


157.54 

123.73 

25.48 


.340 
,433 
2.10 


i 
181.63 
142.65 
29.38 


ewts* 

400 
314.16 

04.40 


000 

00 




425 
380 
340 


2502 
2001 
1600 


22.33 

17.86 
14.28 


2.40 
3.00 
3.74 


25.75 
20.59 
16.47 


56.40 
45.36 
36.31 


No. 1 
2 
3 

4 
5 

6 

7 
8 
9 


300 

284 
259 


1245 
1117 

928 


11.12 

9.97 
8.28 


4.81 
5.37 

6.40 


12.82 

11 .49 

9.55 


28.27 
25.33 
20.07 


238 
220 
203 


783 
670 
570 


6.99 
5.98 
5.09 


7.65 

8.96 

10.52 


8.00 
6.90 
5.86 

4.61 
3.86 
3.12 

2.55 
2.05 
1.68 

1.2S 
.98 
.73 


17.79 
15.20 
12.94 

10.17 

8.55 
6.88 


180 
165 
148 


448 
376 
303 


4.00 
,3.35 
2.71 


13.38 
16.39 
19.79 


10 

11 
12 

13 

It 
15 

IT 

17 

1 1S 


134 
120 
109 


249 
199 
164 


2.22 

5L78 
1.46 


24.14 
30.10 
36.49 


5.64 
4.52 
3.73 

2.83 
2.16 

1.62 

1.32 

... | 


95 
S3 
72 


124 
95 

72 


1.11 

.85 
.64 


48.01 
62.93 
83.65 


65 

58 
49 


58 
46.58 
33.17 


.52 


102.6 


.59 , 
... 1 
... 


19 

20 
21 
22 


4 2 
35 
32 

28 


24.35 
17.93 
14.11 

10.70 






1" 
... 



144 



MANUAL OF TELEGRAPHY. 



TABLE VI. 



One nautical or geographic mile av 

One statute mile, 

One " " 

One nautical mile equal?, 

One statute " " 

One metre equals, 

One metre equals 

One " " 



2029 yds. 

17(30 " 

5280 ft. 

(statute miles) 1.153. 
Nautical miles) .8671 

39.37 in. 

3.281 ft. 

1.094 yds. 

One metre equals three feet, three inches and a third nearly. 

One kilometer equals (100 metres) (Statute miles, .6214. 

One " " (Nautical miles) .539. 

One millimeter (thousandth of a metre) equals .03937 in. 

One gramme equals 15.44 grn?, 

One kilogramme (100 grammes) 2.205 \h±. 



TABLE OF UNITS. 



Unit of ^Resistance, 

One million ohms, 

One millionth of an ohm. 

Unit of tension, 

One million volts, 
One millionth of a volt, 
Unit of quantity, 
One million farads, 
One millionth of a farad, 
Unit of current, 



1 ohm. 
1 megohm. 
1 microhm. 
1 volt, 
1 megavolt. 
1 microvolt. 
1 farad. 
1 megafarad. 
1 microfarad. 
1 farad per second, 




UNION 

pi College 



C. A. SHEARMAN. A. G. SHEARMAN, 

Pres. and Busines Manager. Proprietor. 



Acknowledged by all to be the 
IN THE UNITED STATES. 



Established in 1862. Reffitted in 1S68. Enlarged and 
Re-furuished in 1872. 



SCHOLARSHIP, TIME UNLIMITED: $35. 



Iu connection -with this College is the 

OVER FIFTY MILES IN LENGTH. 

Which is woiked exclusively by the students of the College, thereby enabling 

them to put in actual practice the Theory taught at the College. Students 

arc required to make good copy of twenty-two words per minute 

and manipulate at the rate of twenty-five per minute 
on a four mile circuit, before taking charge of an office on the Hue. 

For further particulars send for our "Telegraph Reporter." 

C.A. SHEARMAN, President. 



L. G. TILLOTSON. E. S. GREELEY. 

L. G. TILLOTSON & CO. 

No. 8 Dey Street, 

NEW YORK, 



MANUFACTURERS OF 



TELEGRAPH MACHINERY 

AND 

Materials of all Descriptions. 

AND DEALERS IN 

GALVANIZED and PLAIN WIRE, 

OF THE VERY BEST UUALITY. 

At the Lowest Rates. 

GLASS INSULATORS AND BRACKETS. 



All Illustrations of Telegraph Instruments in this 
book represent those manufactured by the 
above named firm. Parties wishing any- 
thing in the way of Supplies or In- 
struments, thould address them 
for price list and particulars. 



MANUFACTORY 139, 141 and 143 CENTRE STREET, 

SALESROOM, 8 DEY STREET; 

NEW YORK 






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